Dex's book is not on the couch after he returns from his conversation with Syd by the wall.
When Dex and Syd are at her office, and Dex bends down after knocking over of a few baskets, you can see his strap-on belly.
When Beth and Dex are in the car together, she drives really fast and during a shot of the car speeding, we see a different person driving the car before it switches back to Beth speeding.
When Dex is in Syd's office and she is printing out the pickup timetable, the inkjet printer makes a dot matrix printer sound.
When you first see Syd she's playing the drums. Watch closely and you'll see that the sound doesn't really match.