About halfway through the episode, as Michael goes to erase the security camera footage, you see the computer's screen saver is activated. The camera cuts to the screen, and the "white noise" comes up to show that it's been erased. But when the camera pans back out for the guy sitting at the desk to say "Nothing's coming up," the screen saver's back on the computer.
When Sam finds the proof that Melanie is really J.D. Blake's daughter, an old apartment lease, Mike opens with "An apartment lease from 1985?" but when the camera shows the lease, it is very clearly from 1982, with the date 6/7/82 next to each of the three signatures on it.
When Sam is guiding Micheal through the gallery unseen he incorrectly tells him to go "left" exposing him to the security cameras for a moment. He quickly realizes his mistake saying "My left not yours". The direction Micheal goes is "left" from neither of their perspectives. This is ultimately irrelevant however as the column Micheal is hiding behind is center frame when he moves and both directions would have exposed him.