I think there may be an existing bug report for this.
[addendum: Found it! https://forum.inaturalist.org/t/perpetual-sync-activity/14406/ ]
[second addendum: actually, there’s SEVERAL bug reports on it:
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 ]
[third addendum: https://forum.inaturalist.org/t/updating-1-of-8-observations-android-app/4821 ]