Change ID Is Invalid
Either a Hyper-V Standard or a Hyper-V Rapid Recovery backup has the following warning:
The Change ID of ___ is invalid. Therefore, the differential/incremental changes made on the VM could not be calculated. Forcing a full backup.
This warning may appear repeatedly or it may occur once and be followed by a successful backup. If the former, please follow the resolution steps provided in this article.
Explanation
For pre-2016 Hyper-V backups, Intronis tracks changes to virtual machines using our changed-block tracking (CBT) driver, called VHDTrack. When the change ID of a virtual machine becomes invalid, the CBT driver is unable to capture all the changes to that virtual machine's disks and must force a full backup to guarantee restorability.
Resolution
In most cases, the Backup Agent will force a full backup and the change ID warning will go away. If it does not, however, you can reset the CBT driver to force a full backup.
Note: The steps outlined below will reset the CBT driver tracking changes on all virtual machines. After resetting the CBT driver, a full backup will be forced for all virtual machines, not just the one(s) giving the change ID warning.
Before undertaking this procedure, make sure there are no Hyper-V backups running.
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Open an elevated command prompt and run the command:
fltmc unload vhdtrack -
Expose hidden folders by going to Control Panel → Folder Options → View and checking the option for Show hidden files, folders, and drives.
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Go to the volume(s) where your Hyper-V host's virtual machine files are and delete the folder named $VHDTrack$Store$.
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Reload the VHDTrack driver by running the command:
fltmc load vhdtrack