When Oliver is stuck under the floor, he is lying perpendicular to the loose board that comes down and hits him whenever someone steps on it. The fire department arrives and begins spraying water under the floor parallel to the loose board. However, the stream of water is seen coming from behind Oliver and over his shoulder, instead of from the side, which would indicate Oliver is parallel to the loose board.
When Oliver is on the phone in the hotel room Lisa walks over sits beside the wardrobe, and can be slightly seen in the edge of the mirror and when Arnold turns on the TV and Oliver tells him to turn it off, Lisa can be seen Standing holding the wardrobe door open, but when the shot goes back to Oliver you can clearly see in the mirror that the wardrobe is closed and Lisa is sitting beside it, her knees can be seen in the edge of the mirror.