There's Just No Accounting... - S2-E18
Continuity mistake: While the kidnappers try to grab the judge's son, Bill drives up and stops them. When one of the kidnappers flees the scene Bill takes off after him, and as Bill rams his car into the kidnapper's car, Bill's car is entirely different. Then it reverts back to the original car. (00:31:00)
Continuity mistake: A woman tells Bill that her blind neighbor, Judy, is still in the burning building. In the following shot, when Tanner approaches the door there's a pane of glass beside the door knob and there's a backplate behind the knob, but in the next closeup both the pane of glass and the backplate have vanished. (00:03:45)
Continuity mistake: While Ralph is searching for the missing boy and finds Johnny's baseball cap, Ralph's watch vanishes and reappears, then it happens again when he finds the boy. (00:38:20)
Continuity mistake: At the rec center, when Ralph enters the reserved racquetball court two men force him onto the floor for another polygraph. Ralph's wearing striped socks, blue shorts with white stripes, a blue half-shirt with red/white stripes that bares his midriff, but in the closeups as Ralph sits down and has the polygraph hooked up, all the stripes on his clothing have vanished and Ralph's abdomen suddenly has a significant amount of dark hair. (00:20:55)