Knight Rider [Pilot; a.k.a. Knight of the Phoenix] (1) - S1-E1
Revealing mistake: When KITT takes part in the race and goes up on two wheels, you can see that the stunt driver is behind the wheel and that a dummy is strapped into the passenger's seat.
Plot hole: Laura successfully knocks out both bad guys, steals their van and crashes through the warehouse doors. The van doesn't stall, but inexplicably, she stops it, gets out and runs away on foot, even though the baddies are coming to and coming after her. Not the option you'd expect a kidnap victim to choose: most people would floor it and keep on driving. (00:23:40)
Other mistake: T.J. Hooker and Vince Romano pursue two men who robbed the box office during a Beach Boys concert. The action takes place in the lobby of the Los Angeles Sports Arena, which is an indoor venue, but the footage of the Beach Boys performing is from an outdoor concert.
The Butler Did It (A Bird in the Hand) - S1-E3
Audio problem: In the first scene, we see a quartet led by a sax player. The music we hear, however, is of a trio without sax. This is fixed in the rebroadcast where the song is Satin Doll led by the sax. Additionally, the piano now sounds like an electric to match its look.