and now that I have Duplicati back on 2.0.9.101, I can repro the issue with drive root backup, however here I’m using a 100 MB VHD instead of my actual C:\ drive, that I prefer to backup:
EDIT 1:
This is the same job that worked on 2.0.8.1. --snapshot-policy=On. I did use some exclude filters to keep Duplicati from going where it shouldn’t, derived from my actual C:\ drive backup, however 2.0.9.101 fails with or without them, basically emptying out new backup. Fortunately, versions before the problem were still around. I probably should have just deleted new version, however what I actually did was to run the job on 2.0.8.1 which probably just reattached blocks. Problem was that it took almost as long as an initial backup, which on this system is multi-days.