Server timeout too soon

I am using TLJH. The server timeout is set to 15 minutes. I have verified that if I sit idle for 15 minutes, the server does indeed shut down. However, I and my users have experienced instances where the server shuts down after only a few minutes of idle. I’m unable to reproduce the problem consistently; it just happens. Unfortunately, those are the times when I don’t have logging enabled.

What can I look for to debug and solve this problem?