We started a vanilla 1.16.1 server after years of playing modpacks. But we noticed sometimes when people would join, they would get in, and it would work for about 2 seconds (chat would work, other players could see the person walk), and then they would get the generic Internal Exception error. Yesterday it seemed that each player restarting their PC would fix it, but today even restarts wouldn't work. Any idea what could be causing it? the server has 4 gigs of ram allocated and the usage never went above half.