the reason is not important. do not use miner restart. AMD drivers is the major factor anyways. Instead do system reboot using "-r 1" flag and reboot.bat (in the same folder) with the following content: "shutdown /r /t 5 /f".
I have created reboot.sh with "reboot -f" command in Claymore's program folder.
But problem ist if I test it:
sudo reboot -f
or
sudo shutdown -r
the rig does not reboot but it freezes with black screen instead. I have to physically switch off the power to start it again.