Problem with backup since update?

Regarding the error popup Could not find file ‘D:\Dropbox\.dropbox.cache’. how is Dropbox involved in this?

What version are you running now? You can find that in ServerVersion, in MENU --> About --> System info

EDIT: I might have found a regression introduced in 2.0.4.3. Based on dates, maybe you got that or 2.0.4.4.
Did you move this entire user profile to D:? Dropbox usually puts its folder in one, and its cache inside that. Duplicati has never liked to see excess items in its backup folder, although possibly its sensitivity increased.

Found 1 remote files that are not recorded in local storage, please run repair is what versions before your Could not find file would have done, so that error turned into a different error…

The code-level details of what I think might be a regression are maybe here due to some too-similar names:

- foreach (string s in System.IO.Directory.EnumerateFiles(m_path))
+ foreach (string s in systemIO.EnumerateFileSystemEntries(m_path))

Regardless, the call gets directories too, impacting later code such as FileEntry that didn’t find such a “file”.
This shows the introduction in 2.0.4.3, in Fixed IO calls in Filebackend. amidst much other change.
This was the same symptom reported in 2.0.4.1, but I haven’t gone back that far to test. Code appears fine.

Let me see what @verhoek thinks.

Meanwhile, could backup go into a subfolder of Dropbox, or use the Dropbox storage type instead of files? Downgrade to 2.0.4.2 might also be an option, and might prove more completely when this problem began.