What’s this new post? Is the issue a process death (should be easy to see, even if mysterious) or not?
EDIT:
If you see a working Duplicati UI in the web browser, you still have a Duplicati process (technically two because the first one looks for the most recent update and runs it, then the child does the actual work).
Task Manager also shows processes. I think a true Duplicati death will also close TrayIcon if you use it.