Internet mode crashes Urbackup Server

If I activate Internet mode urbackupsrv crashes without writing an error to /var/log/urbackup.log

Below is the log starting with the daemon restart to activate internet mode and the restarts to deactivate it.
Is there a way to get a more detailed log?

Steps to reproduce on my machine:
1 activate internet mode in the website
2 sudo systemctl restart urbackupsrv
3 website is rechable and urbackup seems to work normally
4 wait several minutes
5 website is no longer reacable an acording to top the urbackupsrv is no longer running

Steps to repair (also in log)
1 sudo systemctl restart urbackupsrv (no message in log)
2 deactivate internet mode in website
3 sudo systemctl restart urbackupsrv (this one is in the logfile)

UrBackup 2.4.13
Ubuntu 20.04.3 LTS (GNU/Linux 5.4.0-94-generic x86_64)
VM in Proxmox

2022-01-21 13:20:49: WARNING: Shutting down (Signal 15)
2022-01-21 13:22:37: WARNING: Restarting shadow copy of C:\ because it was started by this server
2022-01-21 13:29:31: WARNING: Shutting down (Signal 15)