I made a lot of attempts trying to beat "the dance room" in order to get last remaining secret on level 7 behind the iron door.
I finally managed to catch all shots (I'm pretty sure I didn't miss any) but for some reason I was teleported behind the iron grate as usual, and iron door didn't open. It was kind of frustrating... Could it be some kind of glitch? The missed shots counder didn't reset properly between quicksaves or something.
Yes, maybe it wasn't exactly fair on my part to try and ease things a bit by quicksaving and quickloading in the middle of the dance, but after iron door didn't open either, I made only "fair" attempts, performed in one go. The last fair and successful attempt was the one I described in the first paragraph.
I'm kind of worried the next successful attempt might also be fruitless. My inner perfectionist doesn't allow simply to go and skip this secret

Can anything be done to solve this predicament?