“Session interrupted” notifications generally occur when there is a network issue between the Virtual Apps server or desktop and the client terminal. I would run through a process of elimination to see if the issue only happens at a specific user location, with specific endpoint clients, with specific Receiver versions and so on.
You could also monitor the VDAs and check to see if there are TCP connection drops being reported. Have your network team run tests on the networking devices that are client-side to see if there is any packet loss.