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.
Frequently, the camera angle from inside the cab of Squad 51 (usually on the passenger side) shows a rear-view mirror prominently in the upper-left corner of the screen, even though the Squad 51 vehicle itself doesn't have a rear-view mirror.
Because the exterior shots of the station were from an active working LAFD station(127), Truck-127 was parked off to the side of the station during filming, and during several of the response clips you can see parts of the actual truck to the right of the building.