Created attachment 122098 [details]
Images depicting the situation on a OneDrive synced folder

Calc creates a lock-file for CSV files opened. This lock file causes sync error in OneDrive for Business-synced folders. OneDrive for Business complains about unsupported characters in the file name.

The nomenclature for the files is such:
CSV-file: pois_ekstra.csv
Lock file: .~lock.pois_ekstra.csv#

I found this link to a KB discussing invalid characters in filenames in OneDrive
https://support.microsoft.com/en-us/kb/2933738

There seems to be a problem with both the '~' and '#' characters in the lock file filename.

Resolving the issue is not easy. In my case the lock file seems to be a remnant of a stale Calc session, or more likely a remnant of an incident when Calc was runing and I shut down the computer forcefully by holding the Off-button until power off. Also a run-out battery might have caused the file to linger.

In any account the file does not show in the file list in Windows Explorer on Windows 7 with standard settings. I turned on 'Show hidden files, folders and volumes' to make it show up. Most users are oblivious of this setting, and so the error is mysterious, with no way to fix the sync error; OneDrive seems to complaining about an error in a filename of a file which is not present in the filesystem anymore.

I found a work-around: 
By adding a '.tmp' suffix to the filename, the sync error disappeared. This is due to the fact that OneDrive for Business does not even try to sync files with a '.tmp' suffix. I extracted this information from the help info for the sync error (Norwegian only, no URI, sorry): 
Du kan ikke laste opp OneNote-filer eller *TMP- eller *DS_Store-filtyper. Du kan heller ikke laste opp desktop.ini, tomlene.db eller ehthumbs.db.

Hence this nomenclature would work:
CSV-file: pois_ekstra.csv
Lock file: .~lock.pois_ekstra.csv#.tmp