When I slowly pull down to refresh, I see the UIActivityIndicator circle slowly get more complete before it starts the refresh. Just before the circle is complete and the refre
I would need to see the rest of your code (or at least the scrolling + refreshing methods) to diagnose the problem.
Here's our tutorial for implementing custom pull to refresh controls in objective-c and swift. If you follow this tutorial you shouldn't see any jumping or jerking.
http://www.jackrabbitmobile.com/design/ios-custom-pull-to-refresh-control/
Hope it helps!