Client computer shuts down not within backup window

The backup is working great with one Urbackup server and a few client machines. One of the requirements is that one of the client machines (windows 10) will be turned off when the backup is done. This client machine is turned on the next morning 8-9.

My problem is that somehow shutdown occurs randomly with a proper message outside of the backup window hours.

Details:

Backup window: Sun-Fri/20:30-6:00

Interval for incremental file backups: 5

Created postfilebackup.bat file with one line: shutdown /s

The client is turned on every morning between 8 and 9 in the morning.

I need to have this machine backed up (incremental file backup) once a day and be turned off when it’s done. Any suggestions will be appreciated.