The distance between Snix and the riding mower kid changes between shots (from being caught up to him, only to be far behind again).
During the climatic fight between Snix and Jim, the couch changes position.
The windows outside switch daylight, during the climatic fight between Snix and Jim.
The way Snix's body is thrown out the window and lands on the ground between two different shots.
When Jim is talking on the phone, you can see the hole in the phone as the cord was unplugged and scotch-taped onto the speaker - this was to avoid receiving a dual tone while trying to perform the actor's dialog.
Jim is talking to Xins and he's told by him to face Snix himself, when the shot switches from Jim back to Xins, you can hear a page flip - revealing an obvious script that the voice actor is recording over.
When the riding mower kid gets chased into the forest by Snix, the sounds (including the rain and thunder) indicate that he's in a tropical rainforest - even though he clearly isn't.
When Snix takes the box, dumps it out into the toilet and flushes the material down the toilet, you can briefly seen the cameraman's shadow moving across the toilet - apparently trying to get a close-up.