On 14/02/2020 13:21, David Kastrup wrote:
  I think there are some emergency SysReq key
combinations.  No idea
 whether they need some special enabling.  They bypass user space and
 might be worth a try for getting a somewhat more regular shutdown. 
Alt + SysReq + REISUB (aka "Reboot Even If System Utterly Broken")
should reboot the machine.
Best,
Jeremy