This may be related to this problem - https://forum.inaturalist.org/t/observations-failed-to-add-to-habitats-s-afr-project-in-web-uploader/8682
and in extreme cases, this problem:
https://forum.inaturalist.org/t/not-all-observations-uploading/4946/86?u=karoopixie
which causes observations to not index and look as if they haven’t uploaded at all.