in season 5 episode titled "4x4" describes four cases being investigated seperately in the episode where the events were continually rewinded until the whole night unwinds... (to be specific.. the episode where Greg and Sarah take a decontamination bath)...

in episode, the events are recorded in differnt angles throughout the night.... there were two scenes in which Nick is on the phone asking the Butterfield Academy for their roster and Catherine looks at him as they cross paths. one story follows Catherine after they cross paths, and the other follows Nick.

the two scenes were clearly trying to depict the same event, however, in the first scene, you can see Nick walking on the left of Catherine... but in the second scene, Nick passes first and walks on the right of Catherine.