Wheeler has to hot-wire the ambulances in order to get them going. However, when Dr. Chase has to get in the ambulance for a quick get-a-way later in the film, there are keys in the ignition and she easily turns it over.
When the first infected is shot off of the bus,there is a blood stain on the windshield and you cannot see out. In the next scene they approach a woman asking for help in the street and you can see through the windshield. In the scene after that the blood is back on the windshield.
When stealing the second ambulance, the passenger side window is smashed, but in later scenes it has returned unbroken.
When Gunner enters the bus right before he finds his wife, one of the dead bodies changes his seating position.
Dr. Chase is able to dial a number into a touch screen phone while wearing thick rubber hazmat gloves. This is of course impossible.
There are several situations in the film where night vision could help the characters in dark areas, still, it is only used in one scene.