I’ve been in farming worlds a lot, and sometimes there’s a trapdoor in order to shoot enemies.
The trapdoor is open for me, so I start shooting, and another player comes and closes the trapdoor. The player starts shooting against which on my screen is closed, a trapdoor, but then the player starts killing enemies.
I’m pretty sure there’s a bug with doors and trapdoors if you leave them open and exit the world, and no one else is in the world. I don’t think that happens with doors that have switches, but with normal doors/trapdoors.
The bug makes the door/trapdoor open for some players, and closed for some players.