Really, I'd think the big problem is that knock takes ten minutes.
Also, while telling the party there's monsters coming from the sounds is fine, telling them "Oh, and SUDDENLY THERE'S TEN MILLION MONSTERS BECAUSE YOU GUYS BROKE MY RULES D:<" is not.
Lastly, yeah...yeah, what happened to "REAL WORLD? PSH MORE LIKE BORING WORLD, WE'RE FANTASY HEROES, HOOOOOOOOOOOO!" there, eh? So I can kill a towering and murderous dragon who was powerful and wise decades before I was even born, a veritable avatar of destruction, but...I can't quite handle a door?