At one point, we see a shadow of a building on the side of the bus, but in the next wide angle shot, there are no buildings around.
(at around 1h 7 mins) When Ruby falls and hits her head on the rock, it gives way like rubber.
(at around 43 mins) Pluto is supposed to be holding on to the rope that is dragging behind The Reaper's bike. But, at one point, both of his hands are off the rope, indicating that it's attached to his body and dragging him along.
(at around 53 mins) When Hulk gets shot off the bike with the crossbow the cable that pulls him from the bike is clearly visible.
(at around 1h 5 mins) Ruby says that The Reaper is Papa Jupiter's big brother, but in The Hills Have Eyes (1977), Otis (Jupiter's father) explained that Jupiter only had an older sister who later died in a house fire that Jupiter set.