This is how I add my geofences:

public void setGeofenceRequest(Location location) {
    if (geofences == null) {
        geofences = new ArrayList<Geofence>();
    }
    geofences.add(new Geofence.Builder()
            .setRequestId("3")
            .setTransitionTypes(Geofence.GEOFENCE_TRANSITION_EXIT)
            .setCircularRegion(
                    location.getLatitude(), location.getLongitude(), PSLocationService.getInstance(context).kPSGeofencingDistanceMedium)
            .setExpirationDuration(Geofence.NEVER_EXPIRE)
            .build());
    Intent intent = new Intent(context, ReceiveTransitionsBroadcastReceiver.class);
    PendingIntent pi = PendingIntent.getBroadcast(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
    if (geofences.size() > 0) {
        LocationServices.GeofencingApi.addGeofences(mLocationClient, geofences, pi);
        Log.i("", "geof autopilot2 will set geofence for autopilot-3");
    }
}

And this is my BroadcastReceiver. Where I should receive them:

public class ReceiveTransitionsBroadcastReceiver extends BroadcastReceiver {

@Override
public void onReceive(Context ctx, Intent intent) {
    Log.i("","autopilot valid geof on receive transisionts broadcast receiver");
    PSMotionService.getInstance(ctx).buildGoogleApiClient();
    GeofencingEvent geofencingEvent = GeofencingEvent.fromIntent(intent);
    int transitionType = geofencingEvent.getGeofenceTransition();
    Location geofenceCenter = PSApplicationClass.getInstance().pref.getGeoCenter(ctx);
    if(geofencingEvent.getTriggeringLocation() != null) {
        if (geofenceCenter != null) {
            Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver TRIGGERING LOCATION: " + geofencingEvent.getTriggeringLocation().toString() + " / GEOFENCE CENTER: " + geofenceCenter.getLatitude() + ", " + geofenceCenter.getLongitude(), "D", Constants.TRACKER);
        } else
            Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver TRIGGERING LOCATION: " + geofencingEvent.getTriggeringLocation().toString(), "D", Constants.TRACKER);
    }else Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver ERROR => TRIGGERING LOCATION NULL", "D", Constants.TRACKER);
    if(transitionType == Geofence.GEOFENCE_TRANSITION_EXIT) {
        List<Geofence> triggerList = geofencingEvent.getTriggeringGeofences();
        for (Geofence geofence : triggerList) {
            Log.i("", "geof is s receive transition broadcast receiver " + transitionType + " GPS zone " + geofence.getRequestId());
            if(geofence.getRequestId().contentEquals("3")) {
                Log.i("", "geof autopilot2 ENTERED GEOFENCE will start pilot with first location");
                Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver check to see if should start pilot", "T", Constants.TRACKER);
                PSLocationService.getInstance(ctx).fastGPS = -1;
                PSLocationService.getInstance(ctx).RequestLocationUpdates();
                if(PSTrip.getActiveTrip() != null) {
                    PSLocationService.getInstance(ctx).removeAutoPilotGeofence();
                }else PSMotionService.getInstance(ctx).checkinTime = System.currentTimeMillis() / 1000;
            }
        }
    }
}
}

Now usually it works, but not always. I would say that only about 75% of the time it should work, the geofence events are actually called. I feel like the more time since I've set the geofence, the less likely it will be to be called. Why is this happening? Is the triggering event also being dismissed, when the app is cleaned by the garbage collector? How can I make it so that my geofence is always being called, when the case?

EDIT:

This is my defaultConfig:

 defaultConfig {
    minSdkVersion 15
    targetSdkVersion 23

    ndk {
        moduleName "ndkVidyoSample"
    }
}

I changed from a Broadcast Receiver to a IntentService:

public class PSGeofenceTransitionsIntentService extends IntentService {
private static ActivityManager manager;
private static PSGeofenceTransitionsIntentService instance;
private GeofencingClient mGeofencingClient;
Context context;
private PendingIntent mGeofencePendingIntent;
public static boolean isMyServiceRunning(Class<?> serviceClass) {
    for (ActivityManager.RunningServiceInfo service : manager.getRunningServices(Integer.MAX_VALUE)) {
        if (serviceClass.getName().equals(service.service.getClassName())) {
            return true;
        }
    }
    return false;
}
public static PSGeofenceTransitionsIntentService getInstance(Context context) {
    if (instance == null) {
        // Create the instance
        instance = new PSGeofenceTransitionsIntentService(context);
    }
    if (!isMyServiceRunning(PSGeofenceTransitionsIntentService.class)) {
        Intent bindIntent = new Intent(context, PSGeofenceTransitionsIntentService.class);
        context.startService(bindIntent);
    }
    // Return the instance
    return instance;
}
public PSGeofenceTransitionsIntentService() {
    super("GeofenceTransitionsIntentService");
}
public PSGeofenceTransitionsIntentService(Context context) {
    super("GeofenceTransitionsIntentService");
    mGeofencingClient = LocationServices.getGeofencingClient(context);
    manager = (ActivityManager) context.getSystemService(Context.ACTIVITY_SERVICE);
    instance = this;
    this.context = context;
}
protected void onHandleIntent(Intent intent) {
    Log.i("", "autopilot valid geof on receive transisionts broadcast receiver");
    PSMotionService.getInstance(context).buildGoogleApiClient();
    GeofencingEvent geofencingEvent = GeofencingEvent.fromIntent(intent);
    int transitionType = geofencingEvent.getGeofenceTransition();
    Location geofenceCenter = PSApplicationClass.getInstance().pref.getGeoCenter(context);
    if (geofencingEvent.getTriggeringLocation() != null) {
        if (geofenceCenter != null) {
            Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver TRIGGERING LOCATION: " + geofencingEvent.getTriggeringLocation().toString() + " / GEOFENCE CENTER: " + geofenceCenter.getLatitude() + ", " + geofenceCenter.getLongitude(), "D", Constants.TRACKER);
        } else
            Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver TRIGGERING LOCATION: " + geofencingEvent.getTriggeringLocation().toString(), "D", Constants.TRACKER);
    } else
        Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver ERROR => TRIGGERING LOCATION NULL", "D", Constants.TRACKER);
    if (transitionType == Geofence.GEOFENCE_TRANSITION_EXIT) {
        List<Geofence> triggerList = geofencingEvent.getTriggeringGeofences();
        for (Geofence geofence : triggerList) {
            Log.i("", "geof is s receive transition broadcast receiver " + transitionType + " GPS zone " + geofence.getRequestId());
            if (geofence.getRequestId().contentEquals("3")) {
                Log.i("", "geof autopilot2 ENTERED GEOFENCE will start pilot with first location");
                Utils.appendLog("GEOFENCE ENTERED ReceiveTransitionsBroadcastReceiver check to see if should start pilot", "T", Constants.TRACKER);
                PSLocationService.getInstance(context).isLocationRequestsOn = -1;
                PSLocationService.getInstance(context).RequestLocationUpdates();
                if (PSTrip.getActiveTrip() != null) {
                    removeAutoPilotGeofence();
                } else
                    PSMotionService.getInstance(context).checkinTime = System.currentTimeMillis() / 1000;
            }
        }
    }
}
public void removeAutoPilotGeofence() {
    try {
        Log.i("", "autopilot remove autopilot geofence");
        List<String> list = new ArrayList<String>();
        list.add("3");
        if(mGeofencingClient == null)
            mGeofencingClient = LocationServices.getGeofencingClient(context);
        mGeofencingClient.removeGeofences(list).addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void aVoid) {
                Utils.appendLog("GEOFENCE removeAutoPilotGeofence Success removing geofences!", "I", Constants.TRACKER);
                Log.i("", "GEOFENCE removeAutoPilotGeofence Success removing geofences!");
                PSApplicationClass.getInstance().pref.setGeoCenterString(context, "-1");
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Utils.appendLog("GEOFENCE removeAutoPilotGeofence FAILURE removing geofences!" + e.getMessage(), "I", Constants.TRACKER);
                Log.i("", "GEOFENCE removeAutoPilotGeofence FAILURE removing geofences!" + e.getMessage());
            }
        });
        Utils.appendLog("GEOFENCE: Disabling geofence done removeAutoPilotGeofence", "E", Constants.TRACKER);
    } catch (final Exception e) {
        if (e.getMessage().contains("GoogleApiClient") && e.getMessage().contains("not connected")) {
            PSLocationService.getInstance(context).startLocationClient();
            Handler han = new Handler();
            han.postDelayed(new Runnable() {
                @Override
                public void run() {
                    Utils.appendLog("autopilot2 error will try again", "E", Constants.TRACKER);
                    removeAutoPilotGeofence();
                }
            }, 1000);
        }
        Log.i("", "autopilot2 error replaceFragment autopilot geofence:" + e.getMessage());
        Utils.appendLog("autopilot2 error replaceFragment autopilot geofence:" + e.getMessage(), "E", Constants.TRACKER);
    }
}
public void setGeofenceRequest(final Location location) {
    ArrayList geofences = new ArrayList<>();
    geofences.add(new Geofence.Builder()
            .setRequestId("3")
            .setTransitionTypes(Geofence.GEOFENCE_TRANSITION_EXIT)
            .setCircularRegion(
                    location.getLatitude(), location.getLongitude(), PSLocationService.kPSGeofencingDistanceMedium)
            .setExpirationDuration(Geofence.NEVER_EXPIRE)
            .build());
    //ADDING GEOFENCES
    if (geofences.size() > 0) {
        if(mGeofencingClient == null)
            mGeofencingClient = LocationServices.getGeofencingClient(context);
        mGeofencingClient.addGeofences(getGeofencingRequest(location, geofences), getGeofencePendingIntent()).addOnSuccessListener(new OnSuccessListener<Void>() {
            @Override
            public void onSuccess(Void aVoid) {
                RealmLocation realmLocation = new RealmLocation(location.getLatitude(), location.getLongitude(), location.getTime() / 1000, null, true);
                realmLocation.setAccuracy(location.getAccuracy());
                realmLocation.setSpeed(location.getSpeed());
                PSApplicationClass.getInstance().pref.setGeoCenter(realmLocation, context);
                Utils.appendLog("GEOFENCE setGeofenceRequest Success adding geofences!" + location.getLatitude() + " / " + location.getLongitude(), "I", Constants.TRACKER);
                Log.i("", "GEOFENCE setGeofenceRequest Success adding geofences! " + location.getLatitude() + " / " + location.getLongitude());
                PSLocationService.getInstance(context).stopLocationClient();
                PSMotionService.getInstance(context).buildGoogleApiClient();
            }
        }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                Utils.appendLog("GEOFENCE setGeofenceRequest FAILURE adding geofences!" + e.getMessage(), "I", Constants.TRACKER);
                Log.i("", "GEOFENCE setGeofenceRequest FAILURE adding geofences!" + e.getMessage());
            }
        });
        Log.i("", "geof autopilot2 will set geofence for autopilot-3");
    }
}
/**
 * Gets a PendingIntent to send with the request to add or remove Geofences. Location Services
 * issues the Intent inside this PendingIntent whenever a geofence transition occurs for the
 * current list of geofences.
 *
 * @return A PendingIntent for the IntentService that handles geofence transitions.
 */
private PendingIntent getGeofencePendingIntent() {
    // Reuse the PendingIntent if we already have it.
    if (mGeofencePendingIntent != null) {
        return mGeofencePendingIntent;
    }
    Intent intent = new Intent(context, PSGeofenceTransitionsIntentService.class);
    // We use FLAG_UPDATE_CURRENT so that we get the same pending intent back when calling
    // addGeofences() and removeGeofences().
    return PendingIntent.getService(context, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);
}
/**
 * Builds and returns a GeofencingRequest. Specifies the list of geofences to be monitored.
 * Also specifies how the geofence notifications are initially triggered.
 */
private GeofencingRequest getGeofencingRequest(Location location, ArrayList<Geofence> geofences) {
    GeofencingRequest.Builder builder = new GeofencingRequest.Builder();
    // The INITIAL_TRIGGER_ENTER flag indicates that geofencing service should trigger a
    // GEOFENCE_TRANSITION_ENTER notification when the geofence is added and if the device
    // is already inside that geofence.
    builder.setInitialTrigger(GeofencingRequest.INITIAL_TRIGGER_EXIT);
    // Add the geofences to be monitored by geofencing service.
    builder.addGeofences(geofences);
    // Return a GeofencingRequest.
    return builder.build();
}

}

I have in it also the code to remove and add the geofences, and the listener always goes into onSuccess regarding adding them.

For starters, I would not put this code inside a BroadcastReceiver.

Besides being bad practice, the component might be shutdown before the code has finished executing.

Please consider starting a Service from your Receiver, if you need to run code that might take some time. Otherwise for a short execution time, you may use an IntentService.

By looking at your code, I'm aware of two reasons your Geofences are not working as expected:

1) The nature of Geofences

Geofences API retrieves your location mostly from WiFi / Cellular Data, which is often unavailable.

I tried to use Geofences once, and I found them very inaccurate. I switched to LocationManager making it use pure GPS location and it met my expectations.

Please see this answer, which advises to

Poll the GPS hardware on an interval without doing anything with the result and you'll start getting more accurate geofences.

I have never tried Google's FusedLocation API, but I have heard people saying it worked very well for them.

If you use LocationManager, you will have to implement your 'Geofencing logic' yourself; you can easily do it with Location.distanceTo(Location).

Example:

final float distanceFromCenter = currentLocation.distanceTo(this.destination);

if (distanceFromCenter <= YOUR_RADIUS_IN_METERS) {
   // you are inside your geofence
}

2) CPU is not active

The fact that the Geofences are active, does not necessarily mean that your phone is awake and computing location checks.

To fix that, you can start a ForegroundService from your BroacastReceiver. The Service should hold a partial WakeLock as well. This guarantees that:

The OS does not kill the service (or better: less chance to be killed...)
The user is aware of the service and can dismiss it if necessary
The CPU is running. Therefore you can be sure that the code that retrieves the location is running (please remember to to release the WakeLock when the service stops).

Please note that Android may still kill your service if necessary.

You can find plenty of examples on the web on how to start a ForegroundService from a BroadcastReceiver, how to hold a WakeLock and so on...

Also, check out to the new Android O API, that brought some minor changes to the ForegroundService and other components.

PS: I have developed and application that uses all the components mentioned above (except for the FusedLocation) and I was extremely satisfied.

EDIT: Answering OP's questions

Okey, let's try to make some order here, otherwise future readers may easily get confused. I'll start by answering what written in the original question and the 'bounty banner', then the OP edits, and finally the questions the OP placed in the comments.

1) Original question

Is the triggering event also being dismissed, when the app is cleaned by the garbage collector?

Most probably yes. See this answer where OP implemented a service that runs in a separate process, in order to make geofence be triggered even when the app is killed.

I need to understand what causes the geofences not to get called, if enough time has passed

Plenty of reasons. See my original answer.

I saw an implementation of the geofence logic with an Service instead of a broadcast receiver, will that work better?

A Receiver and a Service are two different things. Please read Android's documentation. You can start a Service from a BroadcastReceiver, which is usually the preferred way to 'receive' PendingIntents and do something with them.

2) Edits

Please note that I did not tell you to replace the BroadcastReceiver with a Service, but that it might be a good idea to start a Service from your Receiver and handle all your logic there.
Making your IntentService a Singleton class is not necessary as (from IntentService documentation)

All requests are handled on a single worker thread -- they may take as long as necessary (and will not block the application's main loop), but only one request will be processed at a time.

Do not store Context into a Singleton class or some static references. I'm impressed Android Studio did not warn you.

3) Comments

I need this to work 24/7 hence I cannot use the location all the time, cause of obvious battery issues.

Please read Android Oreo Background Execution Limits. This might be an issue for you.

Also now that I changed to a intentService, is that enough to ensure it should stay awake?

No, as I said, you probably need a partial WakeLock in order to turn on the CPU.

Do I need to initiate it another way, in order to keep it in the foreground?

Yes. In order to start a Foreground Service, you need to call startForeground(int, Notification)

Please note: IntentServices lifespan is limited to the end of the onHandleIntent() function. They are not supposed to live for more than a few seconds, typically. Use the Service class if you want to start a Foreground.

Moreover, as said in the original answer, a new Foreground API is available and preferred for Android Oreo.