Continuity mistake: Jenna takes one red cup from the 3 stacked next to the higher stack and returns the two cups to her left (and left of the higher stack). Jenna uses her left hand, supported by her right, to handle the bottle of wine, but the 2 cups disappear after she sets the bottle on the table. (00:19:50 - 00:20:14)
Deliberate mistake: There is one vertical board missing between the other parallel boards, but the upper half of the gap is wider and forms a "V" when Mark is videotaping Jenna (who is on the other side of the fence). The missing board, between two parallel boards, has a uniform width from top to bottom. (00:08:40)