A Knight in Shining Armor - S2-E13
Revealing mistake: When Michael fights the bad guy at the end of the episode, it's easy to tell that they're both stunt doubles.
Revealing mistake: The shot of KITT releasing his oil slick at the end of the episode is backwards: "KNIGHT" appears as though it's in a mirror.
Knightmares - S2-E11
Revealing mistake: When Michael and KITT are going to jump at the dam in order to save Cara from drowning in the water container just before they jump you can see a stunt ramp below KITT.
Answer: KITT didn't choose to go off the cliff in Goliath Returns, it just happened as he tried to avoid Goliath. Just 'cus it happened, doesn't mean It's gonna cure his fear of "flying"