Thank you very much, Teus. I have started this issue: https://github.com/bibledit/cloud/issues/780.
I really appreciate all your help and hope that I soon will be
able to not bother you so much.
One possible bit of additional information is that it is possible that a sync with the server was attempted at a point when the server was down for a few minutes for software updates and a reboot. If that was the cause of the flurry of failure messages, then it should have corrected itself with the next sync after the server was up again.