Proxmox unbootable - grub error: disk lvmid/id not found

[Never]

My server was running fine until my second day of travel. In the early hours of that morning I received a message that the device was offline, I thought it was just a power failure at home but when I got home I found out that it wouldn't start up properly.
The error messages:


I tried to enter the rescue mode but it didn't work:

 

[datschlatscher]

This seems to be a grub2 bug that is sometimes triggered with some configurations.

This post has some more information and a possible solution to this problem. Changing something about the LVM config and running update-grub again seems to resolve the problem in the majority of cases.
For more of a step-by-step approach, there is a good guide on how to fix this in the first answer in the post above and in this answer in another thread with the same problem.