Continuity mistake: When Chris and Dani are at the police station and about to have sex, her shirt mysteriously reappears. They are kissing and Chris is shown removing her shirt (leaving her in a red bra). A few seconds later they are still kissing, and you can see that her shirt is back on.
Visible crew/equipment: When Knoxville and a bad guy end up fighting hand to hand downstairs (in Chris's house) after trading off shotgun blasts at one point they end up grappling in front of an armoire with a glass front. Just before they struggle off to fight in another part of the room you can see a crew member with a black shirt appear from the left in the reflection of the glass. Since Chris appears in the scene about a few seconds after this it could be him. He was also wearing a black shirt but one things for sure whoever it was was not meant to be seen as they quickly ducked out of sight.