In the Rescuers down under stash mission, you need to release the brakes in order to reach the end. I have no option to release the brakes, only to sabotage or trap the car, so acquiring that perk seems to bug out the quest, although I didn't have time to check on a car in a different environment. I checked on all sides of the car, I climbed down and climbed back up again multiple times--nothing worked. I even eventually tried sabotaging it in the hopes that the resulting explosion might push it down, but nothing happened.