There is no DEM running as a worker and Orchestrator

I'm have installed vCAC server (or DEM Orchestrator) , DB server, Web server,DEM Workers, but I'm often receive a warning message when log in into the Web.

I'm can see lot of errors related to DEM-Worker, where logs message says "DEM Session ID mismatch - unregistering and re-registering DEM"

I'm restart DEM Orchestrator service and DEM Worker, it is a temporary workaround , but 2 - 10 hours later I'm receive this warning message again.

Help me pls.