If a waypoint hold is in place. say on a getin command for someone to enter a vehicle.. if that vehicle is interrupted in any way such as a player getting in the vehicle before that getin command unit "gets in" The on activation script does not execute.
Video for easier debugging
http://youtu.be/b5-GLd1Fq_M
Please see video for scenario example
in this case a fix was to lock vehicle, and unlock it after loading the weapons, but not sure this is possible in every scenario
Mass closing ancient tickets with no activity for > 12 months; assume fixed or too trivial.
If this issue is still relevant in current dev build, please re-post.