Just FYI (though I’m sure you are already aware of it), the issue seems to be pretty widespread:
https://forum.inaturalist.org/t/android-app-stuck-in-preparing-cleaning-up-syncing-loop/14964
this current thread: https://forum.inaturalist.org/t/perpetual-sync-activity/14406/
https://forum.inaturalist.org/t/android-app-observation-remains-in-sync-loop/13504
https://forum.inaturalist.org/t/sync-issue-on-mobile-app/4866
https://forum.inaturalist.org/t/android-app-doesnt-sync-observations/11777
https://forum.inaturalist.org/t/updating-1-of-8-observations-android-app/4821