I suspect @Jeremy is correct about you possibly having two instances of Duplicati running - if you’ve see both Duplicati on both port 8200 and port 8300 then that’s probably the case.
I do want to point out that historically Duplicati doesn’t lose it’s settings during major Windows updates. They’re actually moved to a backup folder (such as C:\Windows.old) by the Windows update process itself and can relatively easily be moved / copied back to the current Windows folder.
We are considering ways to avoid this externally caused issue in the future but until then here’s how one user handled the situation: