That is a frustrating loop to be in, especially with TrueNAS. Usually, when the VM fails to start after a change, it’s because XCP-ng is trying to pass through a PCI device (like an HBA) that isn't being released properly by the host.
Have you checked if the "hide" parameters in your grub config are still correct? Sometimes an update can reset those, and the host grabs the controller before the VM can. Another thing to try is toggling the BIOS/UEFI mode in the VM settings - TrueNAS can be picky about that depending on which version you’re running.
