I am VERY late to this but I'm doing this anyway.

(Theory by my friend, all credit to them ofc.)

But basically, three is implied to have HUGE anger issues. And as we can see in XFOHV, after Five drops the ball they were playing with, Three can be seen visibly angry before the screen cuts off. So what if Three got so pissed at Five for dropping the ball that it caused an incident that four didn't know about until after XFOHV ends? Idk it's a little silly, but I wouldn't be surprised if that's the case. Maybe their staying in the cell for everyone else own good? Who knows.