Oh boy, I think now I know why there was this big flipping issue, player_box_entrance is actually not what it sounds like, the player uses ai_box_entrance the same way, the AI does ...
No wonder it has playeronly=true, but when I make it to false, the AI does no stop ...
So fixing all those wrong entrances means to touch more than I thought, so it's almost the same work as creating the manual pit stop itself ... meh, codemasters learn to code.
E: So after a few more test I can say: player_box_entrance is utterly useless and not used at all.
Codemasters, seriously. You have two parameters just to not divide AI from player?