Continuity mistake: When Michael is getting Dr. Bergstrom out of Goliath, he steps onto K.I.T.T.'s hood and Bergstrom is to his right, in the next shot Bergstrom is to his left.
Continuity mistake: When Michael and Dr. Bergstrom get out of Goliath, the back door is still open. We see both get into K.I.T.T. at the same time since Bergstrom needs Michael's help walking on the hood. But once they're both in the car, the back door is closed and locked without Michael having a chance to. And if the door can close automatically or remotely, then it should have closed with Michael inside.
Continuity mistake: Right after Michael escapes from his cell, he finds KITT in the garage. Michael has KITT pop his hood to work on him, he asks KITT how he feels, the next shot shows KITT's scanner with the hood down, then it goes back to the shot of Michael and the hood is open again.
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"