Terminals on Windows Server 2012 began to freeze. How to fix it?

Question

System administration

For no apparent reason, users on RDP began to hang in the terminal session.
After working for some time, when you reconnect to the server, a message is displayed The system event notification service is running and login does not occur

In the task manager, disconnecting does not allow you to throw it out of the terminal, only after cutting down all processes, users can reconnect.
1. How to analyze what is happening? What log to watch
2. What to check at the terminals, what can lead to such freezes?

Answer 1

see all))
something like: Microsoft : Windows : Terminal Services and there are a lot of nested
checks starting from the driver and firewall to routing (maybe another IP appeared or something like that)