Confirming this in vanilla java on MacOS. Started a new 1.17 world following the separation into Part 1 & 2. Have upgraded each time no problem. Tonight on upgrade from pre2 to pre3, it works for me, but when my son tried to connect (via Open to LAN, Survival, No cheats)... he gets the above error (in the log, it shows him joining and leaving immediately). He's been connecting in fine up until now. He also is using an unmodded vanilla client, on Windows 10.
JK
Confirming this in vanilla java on MacOS. Started a new 1.17 world following the separation into Part 1 & 2. Have upgraded each time no problem. Tonight on upgrade from pre2 to pre3, it works for me, but when my son tried to connect (via Open to LAN, Survival, No cheats)... he gets the above error (in the log, it shows him joining and leaving immediately). He's been connecting in fine up until now. He also is using an unmodded vanilla client, on Windows 10.