In the beginning Walter has a bagel in the right hand and takes the briefcase with the left hand. In the next shot he's holding the case with his right hand and the bagel in the left hand.
When time slows down, the agent's clothes and hair are moving at the same speed as in normal time; the same for the engine smoke.
When the suitcase is shooting laser beams, one of the lasers hits a street sign from behind as if it's in front of it.
In one shot Walter throws the bagel. But as the camera rises upward, it's still in his hand.