Before the Haunted Mask lunges at Carly Beth, the bottom of Steve's mask can be seen sticking out of his shirt collar, despite the fact that the mask is supposed to be attached to his skin.
Camera shadows in some scenes.
In the first special the shopkeeper tells Carly Beth that if she puts the mask on thrice it won't ever come off (she repeats this in this episode.) He never states that rule applies only to her mask and heavily implies it's for all the masks. She's only able to remove it with a symbol of love because she only put it on twice. However, Steve puts the mask on three times - first in his room to try it on, second to go out, and lastly after scaring Chuck. Even with a symbol of love he should not have been able to remove it a third time.