This problem only happens when FreeFileSync is exiting so it is not a high priority. I am running the keyman 11. Below is the email from FreeFileSync developer. Uninstalling keyman the problem goes away.
FreeFileSync is crashing during exit. The problem is most likely caused by the following DLL which is found in the call stack:
C:\Program Files (x86)\Common Files\Keyman\Keyman Engine 10.0\keyman64.dll
This seems to be a third-party shell extension. Uninstalling or updating to a newer version of this software might help.