Should work as advertised but doesn't always

So I've used this thing about 6 times to hang pictures now, and 5 out of those 6 times I have had to re-hang my picture. I am doing all of the things it tells me to do and when I put the points against the wall I make sure the bubble is right smack in the middle of the level before pressing into the drywall- but 5 out of 6 times it has gone wonky. To be fair- it might be because the floor isn't level. But it could also be because the mechanics of the product aren't quite lined up, so read the other reviews before you decide.

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