You don’t need to have made a screenshot beforehand. If you go to the Restore tab and select any image backup, the layout of any partitions in that backup will be shown at the top of that window. Compare the layout of any pre-upgrade backup to a post-upgrade backup, including the sizes of those partitions. It’s possible that your C drive was shrunk slightly in order to make room for a larger Recovery partition immediately after it. You might also want to check whether the upgrade created any new partitions on your disk, and if so whether you want to include them in your backups going forward. In order for a new backup to be considered a match to an existing backup set (which is required for making a Diff or Inc), the new backup must contain exactly the same partitions as the ones in the existing set. If you add or remove any partitions from your backup selection, or any partitions have been resized and/or rearranged on the source disk, the new backup will no longer be considered a match. The fact that some upgrades within Windows 10 sometimes the resize I described above and therefore trigger unexpected Fulls is why I set my retention policy to apply to all backups in the destination, rather than the default “all matching backups”. Otherwise, the retention policy would no longer act on pre-upgrade backups. But this change means you need to have a destination folder dedicated solely to backups generated by that definition file, otherwise that setting could cause your retention policy to purge completely unrelated backups.