There are a number of stock footage continuity errors. The major one is the differences in Squad 51, which was always a Dodge pickup, but several model years were used on the show. Most of the street scene footage that shows the Squad traveling was shot in Season 1, so an older model usually appears that doesn't always match the Squad that leaves the station or arrives at the scene. Another continuity issue is repetitive use of the same response footage episode to episode, so the same cars are always stopped at the same spot at a particular intersection. Similarly, when the squad only departs from a station in a later episode, the older Crown Fire Coach is shown remaining in the station rather than the current Ward LaFrance.
Crew or equipment visible
The actors portraying the emergency physicians invariably perform the pupil dilation test wrong. When done correctly, your doctor will "swing" the light rhythmically from one eye to the other, noting the response of each pupil. Your pupils should constrict or stay the same size when the light is shone on them. Dilating pupils may alert your doctor to a possible optic nerve problem. On the show, they shine the light into the eye, and very briefly shift it off of the eye and then right back - that's backwards of correct.