Plot hole: At the end of the episode, KITT has to travel about 45 miles in under 8 minutes. That means KITT would have to travel a little under 360 mph for the entire time. KITT couldn't travel that fast until season 4 when he got Super Pursuit Mode, and we never see the speedometer read that high even once.
Continuity mistake: After the photoshoot Michael and Lisa are walking. Lisa's dress is on her shoulder, next shot it's off her shoulder and the shot after that it reappears back on her shoulder.
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"