Thanx, mostly this works, but sometimes we have to fully delete the backups, then rename or at least set the names the same. Deleting all backups is not so sane for this moment, but luckily we’ve backups of the backup thanx btrbk 
In client beta 2.2.2 anyways there seems changes to our problems (just hit the symlink problem, too):
Do not follow symlinks if the symlink target is excluded
Use computer name and serial id to construct default macOS client name
Proper hash send error failure handling in file server UrBackup Server 2.2.3 beta/Client 2.2.2 beta
Is it possible to try beta client 2.2.0 with server 2.1.19, or should we wait for release?