After further reading on the subject, I guess that the problem is the size of over 2 GB. All other thousands of files (incl. hardly further compressible mp3, jpeg, mpeg etc.) are synchronized without problems. Under ubuntu 20.04 LTS the problem did not occur.
After further reading on the subject, I guess that the problem is the size of over 2 GB. All other thousands of files (incl. hardly further compressible mp3, jpeg, mpeg etc.) are synchronized without problems. Under ubuntu 20.04 LTS the problem did not occur.