Visible crew/equipment: When the vehicle drives into the equestrian centre with the brown horsefloat on the back, you can see the shadows of the camera crew on the ground.
Revealing mistake: When KITT is in the valet carpark, he pushes the cars in front of him forwards. It is very obvious they have attached rubber protectors to the bumpers to prevent damage. Also, when KITT is driving by himself 10 seconds later, you can see the stunt man's hands driving the car.
Continuity mistake: When KITT drives off the edge of the cliff, the car changes from a pontiac to another standard car a number of times. When KITT lands, his flight trajectory was from approximately 10 feet, not 100 feet. He should have landed like a belly flop onto the sand, not a shallow dive.
Revealing mistake: Watch the scene where Michael fights two guys for a purse. Michael calls KITT for help. When KITT jumps off a cliff, an old vehicle is the one that jumps off the cliff instead.
Other mistake: When Michael is carrying Micki up the cliff, she's supposed to be unconscious. But he's not holding on to her and her hand stays wrapped around his neck to hold on. Not something she should be able to do. When they're near the top, her hand position changes, but she's still able to hold onto him.
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"