Zsys fails in update-grub after disk is restored with Acronis True Image

For years, I have been backing up my Ubuntu OS using Acronis True Image under Windows 10, and restoring it as needed. This has worked well.

Recently, I started experimenting with Ubuntu 20.04 and zfs on root. I did a full reinstall of Ubuntu on my SSD for this. I naturally backed it up with Acronis under Windows.

At some point, I decided to restore that backup using Acronis.

At that point, zsys started reporting problems when creating snapshots during operations such as "apt install" and "apt remove". A simpler test case is to create a manual snapshot :

root@server10g:/home/madbrain/Desktop# zsysctl save test-snapshot -s
ZSys is adding automatic system snapshot to GRUB menu
ERROR "update-grub" returned an error: exit status 2
root@server10g:/home/madbrain/Desktop#

Is there a workaround for this problem ?

I realize that this is not a common situation, and I should be backing up and restoring zfs snapshots rather than using Acronis, but Acronis has the advantage of having a GUI, and zsys is still experimental. So, I would expect a True Image restore of Ubuntu to still work. Unfortunately, that's not the case. My guess is that there was some sort of partition identifier that was changed during the backup/restore process in Acronis, but I'm not sure what.