Web Console occasionally not responding on port 9090

Hey,

one of our customers reported the following problem:

Every once in a while (1-2 weeks) the web console does not open up because the server is obviously not responding on port 9090 anymore. The server itself works totally fine and if you connect via RDP the SEP console on the server opens up like it should, it's just the web console that doesn't work anymore. When the customer reboots the server everything works again for a couple of weeks. SEP version is 12.1.6 (don't know the exact build number).

Any idea what could cause this behaviour? Are there any log files that could help to find the cause?

Thanks in advance!