but the clients only seems to be disconnected... And someone needs to disconnect them - either the client itself or the server. I would say the later one as a disconnet of one client mostly wouldnt result in a disconnect of all other clients as well.
I am still thinking loud
Is there not a "list" what we can try to exlude possible reasons: I mean what about to disable flhook for 2 days - look if the problem still persist. If not then its flhook related. If yes then the next one, activate flhook and disable anti cheat and do the same observations... Just ideas. I will not demand anything!!!
If there is something i could check on the client side i would give it a try - but i have no idea for what to look. Well i could also try to use a network analyze and monitor the network traffic and see what was send before the disconnect.. Dunno if I would find anything in there or if this could help