CKFetchNotificationChangesOperation sometimes does not return UPDATE, DELETE notifications

Question

CKFetchNotificationChangesOperation returns INSERT operations, but UPDATE and DELETE, not always. DELETE, UPDATE worked last when I submitted app to App Store,

Answer 1

I know this question is old, but for those Googling, be sure to check out this thorough post on the inconsistency of notifications:

Silent pushes not delivered to the app on iOS 11

I found a particularly subtle fix that I mention here.