Revealing mistake: In the Atlanta party scene, we are supposed to believe it starts with a single long take. However there is a sneaky edit when Frank crosses the threshold of the room. He emerges at a slighty quicker pace and his hair is suddenly messed up. (01:10:35)
Suggested correction: There is nothing obvious in this scene that supports this. When he emerges on the other side, he bumps into his friend so suddenly that you can't tell if he was walking at a different pace. The reason his hair is messed up is because he bumps into his friend. He then yells at his friend, jerking his head around as he does so, which messes up his hair even further, which can be seen.
Even if it were true, it wouldn't qualify as a mistake. The shot may be intended to appear as a single shot, but that doesn't mean it's a mistake if it isn't.
Revealing mistake: When Bob Crane was playing drums in the club, the night that he told Patti he and John were going out - he CLEARLY isn't playing to the beat, as you can hear drum fills, and he just playing as hitting the drum once with his left stick.
Revealing mistake: In the opening scene right after she's put in the truck, she is lying on the bed looking in a mirror above her and her earrings are hanging parallel to the ground as though she was standing. (00:02:12)