A cleaner starting point would have been to stop the service, then see if anything was then left over.
I forget whether Duplicati or Windows tends to restart things after manual kills. Basically avoid them.
Is this a new thread for trying to recover from the very hazardous manual deletion of destination files?
If not, where is this starting from? The first line sounds like backup just broke without previous breaks.
EDIT:
If this turns out to be a continuation topic, and first issue was backup failing from a conflict, did you set
auto-cleanup? Though it’s not visible here in stack trace, I mention it as there’s a known issue, and fix.