I had the same situation happen recently. Here are my notes on what I did to fix and resolve. #1 solution is to not run the service, must set it up as a host. This is a pain to make sure the host is always running, but it is the only way to make Advanced (MAS 200) run without users crashing.
MAS 200 Server Configurations
On the Application Server Configuration, go to the Server tab, set KeepAlives = Off
On the Application Server Configuration, go to the Clients tab, set Reconnect = None
On the Application Server Configuration, set the Reconnect to Prompted if wanting to track dropped connections.
On the server, rename \MAS_System\SY_Console.M4T
On the server, rename \home\lib\_appserv\Locate.pvk
On the server, rename \home\lib\_appserv\sessions.pvk
Delete the contents of the MAS90\Locks folder
Delete the MAS200 service and run as a Host program.
To remove all PVXWIN sessions
Close application server
From Task Manager, click to show processes from all users.
Delete pvxwin32.exe sessions
User Maintenance
Go to preferences tab. Check box ""Spawn Tasks from Application Server""
This eliminates Connection Failure to Host message at workstation.