“No wonder the root cause hasn’t been found in so many years: it’s not a bug in the gameserver, it’s a bug in the game.”
The “No user logon” kick has hit Counter-Strike players since at least 2008. An outside developer traced it to a race condition in CS2’s level load loop, and Esportal’s tickets for it dropped from 23% of the daily total to zero. Valve sat on 16 years of complaints. It took an outsider to read them.