Glad you found a solution.
While I understand the way Apple have abstracted apps from 3rd party clound services by making iOS/Files the 'bridge', makes sense from a software architecture perspective (in theory), I've found it so be erratic and unpredicatable with Microsoft OneDrive, Google Drive, Box.com. That's just my experience of course.
So, either all of those companies write bad software, or
The iOS APIs that those 3rd party companies have to use are flaky, or
iOS is bad as acting as the 'bridge'.
I doubt it is the first option 🙂