Propinquity - S3-E20
Continuity mistake: After the ambulance Roy is riding in is involved in a traffic accident, when Johnny arrives he jumps into the back with the injured attendant and patient, and we can see that the stretcher's footrest is light brown. But when the attendants exit, they carry the stretcher out of the back of the first ambulance then wheel it to the second ambulance, and the footrest is now red. It would seem that they merely transferred the patient from the first ambulance's stretcher to the second ambulance's stretcher while still in the ambulance, but they couldn't have done that because two full size stretchers cannot fit into the back of that first station-wagon style ambulance, especially with attendants back there, so they would have had to do the patient transfer on the ground outside. Hence the problem.