I did a little more testing and found that the vehicle seemed to be aborting for saftey when it got confused about the path to take. When I did something reckless like rear-end the vehicle it carried on with no abort.
No, it doesn't do that. There are TWO kinds of "evasive maneuvers":
1) The one that prints a message "aborts due to safety reasons", which ABORTS the service, and CAN be now disabled with the followme_disable_flee = 1 parameter
AND
2) One that doesn't print anything, it goes around your airplane and CONTINUE the service, which is always active and cannot be disabled.
If you set the followme_disable_flee = 1 parameter, you will only see #2, in all cases when there's a problem, like going too close to the car, or not having any other way to reach other than going around you, etc.