Have been using the the bi-directional sync to OneDrive pretty much since it was available. It used, bar the odd quirk be pretty reliable but some where in one of the recent updates it seems to have been tweaked (or MS have changed OneDrive) and now has a stack of issues:
Deleting file on the NAS no longer seems to be transferred to OneDrive. (According to the log the delete is simply ignored.)
Bulk adding files causes issues with only some of the files being transfered to OneDrive other are simply ignored.
It also seems to have developed a problem with files bouncing backwards and forwards. So if you add a file to OneDrive it gets download to local and then promptly a copy is sent back to OneDrive. (You can see this happening in the log)
This means some times when you update a file the file reverts to the old version or you end up with copies of temporary files and application creates during a file modification or save and no original.
I first noticed this problem with OneNote, where the sync process trashes the file and leaves the temp files that should have been reassembled in to a .one file.
I have to save OneNote files in a OneDrive folder that is not sync'd to the NAS.
If you modify the exif info of a jpg in File Explorer you lose the jpg and gain a .tmp file and all sorts of other issues.
The only way to get everything back in sync is to do a restart of the NAS to force a cloud changes scan and a local changes scan which then results in a long list of updates, virtually all NAS to Cloud.
Or alternatively delete the session and recreate it.
