For a long time, I had strange disconnections on the one of my servers.
What's checked:
Spent about one month to find this reason.
By the way, found lot of bugs sensitive to websocket disconnections:
https://github.com/chesslablab/chess-server
So my trip was useful at least for one open source project :)
Ethernet wire and it sockets has limited life time.
If you're old admin, do not forget to check some rusty stuff at first ;)