Stop the DocurecSyc service:
Open Task Manager
Click into the Services tab
Click "Open Services" (or just "Services" if on an older OS)
Find DocurecSync on the list and right click on it and select "Stop"
Ensure no task is left open in the "Details" tab. If there is a task called DocurecSync, right click and select "End Task".
Log in to sage with docurec user credentials, it will ask if you want to disconnect the existing session, select yes.
This error should now be resolved.