I am also on night 11 and I'm having high difficulty trying to juggle between the girls at both of my doors at the same time and repairing broken machines. I've also played the Nightclub a few times thinking it might change the difficulty of admin room but I don't think it did anything.
Update: I've managed to beat night 11 and 12, which is the last night seems like. I guess you just gotta be lucky with the timing of your doors being occupied. For anyone who doesn't know, right clicking will do the same as pressing the return button. Saves a lot of time. Now I gotta figure out how to unlock the rest of the tapes from the board.