I solved this issue like described here: https://apple.stackexchange.com/a/384410
Opened a Terminal and run:
diskutil apfs list
This showed a volume described as "VM" with an error -69461
Then run (replace disk1s4_changeme with your VM volume):
diskutil apfs eraseVolume disk1s4_changeme -name VM
Check that the Volume war recreated and the error ...