This only affects whenever you're in the menu, when trying to join a friend's world.

Whenever a player sets their world max player to 40, and when it gets close to 30 online players, the player count becomes inaccurate. It normally gets stuck on 29/40.

The worst part is that when you try to join, it tries to connect for about 2 minutes and then an error connection comes up "Connection timed out". I've provided all 3 screenshots of the process.

Edit: I also noticed the player count getting stuck on 27/40 and 28/40.

Edit: Still an issue on 1.19.70