HeNotSatisfied

The problem I found was that as soon as the screen is not connected, dimmed or turned off, this behavior occurs. To fix this, I connected an HDMI dummy to the server (LINK). Then the screen power saving settings need to be disabled. This results in a higher power consumption of approx. 0.5~1.5 W for me.
The only way I have found to disable it, which also preserves all hardware functions, is to customize the "GO" file under:
/boot/config/go [usb-drive/config/go].

here the first command under #!/bin/bash must be the command /bin/setterm -blank 0 -powersave off -powerdown 0. The file then looks like this for me:
 
#!/bin/bash #fix kworker bug - keep display active /bin/setterm -blank 0 -powersave off -powerdown 0 # Start the Management Utility /usr/local/sbin/emhttp & the system must then be restarted.

adjusting the go file alone does not solve the problem, it requires an HDMI dummy or monitor.
normally the file "/etc/rc.d/rc.setterm" must be adjusted in Linux Slackware. The lines are already preconfigured and only need to be commented in. See Slackware docs [LINK].
Since unraid creates the /etc/ directory at every start and loads it into RAM, these settings are lost after every restart. 
you can have the file replaced at every start. but i didn't want to do that and i think it's easier to just write the command in the go-file.
go