Think of an app like a voice recorder, for instance; it needs somewhere to store the audio files it creates.
This purpose-based storage model improves user privacy because apps are given access only to the areas of the device's file system that they actually use.
When this first started happening to me on one of my devices I noticed a ton of content not even shared by me to facebook within facebooks androids data folder - com.
Adding some retries might be the easiest fix.
Is there a way to join the page-scoped user ids I get from the messenger notifications with the app-scoped user ids I get from the normal graph api notifications?.
Enthusiasts will dislike it because they may end up needing to jump more hurdles than before to use certain apps.