Photo auto upload disabling itself

I have found on some client devices that from time to time Nextcloud on their iPhones will for no apparent reason disable auto upload of files, which will then also mean I have to reupload every single photo in existence on their phone to get any of the photos it has missed since whenever (and why) it disabled itself from uploading photos and videos from the camera roll. Seems to happen about once every few months on one phone and more seldom on one other. This has happened to my own iPhone once too. Has anyone else experienced this?