Looks like this a more common new issue. Could everyone please add the information mentioned at Having problems with UrBackup? Please read before posting ? E.g. complete (debug level) logs (mostly client logs are interesting), information about operating systems and uncommon software (such as the Bitdefender antivirus).
If you can make memory dumps (in the task manager) of hanging UrBackupClientBackend.exe processes, those would be interesting as well. As well as complete procmon traces, but those might be too large and need to capture not just a hanging process, but what caused it to hang.