They said that after Harry broke his arm in the quidditch match he used his right arm to lean on, even though that was the one that was supposed to be broken.
And they aren't the only ones.
The website movie-mistakes.com has had 11 Chamber of Secrets mistakes reported to it already.
According to other eagle-eyed viewers, the Dursleys' house now looks like it's in a different street and at one point you can see a wire attached to Errol the owl.
They also spotted a mistake when Lockhart falls into the Chamber of Secrets.
He lands with a thump in seconds while Ron and Harry take ages to hit the ground and slide down the pipe instead of falling in a heap.