When Sheila is in front of the firehouse screaming, the window on the driver side of Tommy's truck is open but in another shot the window is closed
When Tommy goes to sleep in the fire truck, it is a new engine 99, but when they are responding to the call later in the show, it is the old engine 99.
When Garrity is talking to Silletti about the girls at the N.A. meeting, the boom mic can be seen above the door.