There are periods in time when a vehicle will drive to close to an object such as a rock or one of those hangers at the airbase. The problem really is that if the AI do hit an object more often then not for me they will not back up and try to change there direction but instead attempt to continue along there path without change and end up begining useless in the middle of combat. The only way ive found to fix the problem is to tell them to move somewhere the opposite direction they where heading and hope they get out of it. also side note ive had a few cases where the AI drove over a rock and the vehicle exploded but i wasnt witness to it as it was going on just the aftermath.