Could you please add some context, such as when it happens, what it looks like, and how Duplicati is left? Knowing how you run Duplicati (Windows service, TrayIcon, Server, etc.) would also help know the picture.
When running Sysinternals tools, note you may need “Run as Administrator” to view privileged processes.
This sounds like the sort of issue that may involve a lock file in control_dir_v2 called lock_v2. I’m not sure.
Win7 Tray Icon Crashing went down that path at first, but the solution wound up being a network change… Curiosity-research after that found (if I recall) issues over how to handle localhost, given IPv6 and DNS.