If you are seeing this message in the VSE log file, it makes me think that the client side is forcibly closing the connection with the VSE:
java.io.IOException: An existing connection was forcibly closed by the remote host
Do you see this behavior during a load test?
Is there something between the client application and the VSE Server? a gateway, load balancer, firewall...
I am wondering if Wireshark would help you in this case. You could start Wireshark in the VSE Server and capture the incoming traffic. Note when you face the issue and take a look at the traffic during that same time.
Hope it helps.
Heloisa