We have tried the profiling branch of Dwarden which improved our FPS so far, but - the issue is still there.
Ping and Desync of players were fine. Server FPS were around 47.
The only information we have found is the following. Everytime a player gets kicked our Server RPT writes:
13:23:02 NetServer::SendMsg: cannot find channel #406545637, users.card=16
13:23:02 NetServer: users.get failed when sending to 406545637
13:23:02 Message not sent - error 0, message ID = ffffffff, to 406545637 (******)
13:23:02 NetServer::SendMsg: cannot find channel #406545637, users.card=16
13:23:02 NetServer: users.get failed when sending to 406545637
13:23:02 Message not sent - error 0, message ID = ffffffff, to 406545637 (******)