After two nasty midair explosions today when attempting to paradrop Humvees from the Chinook. Tried a bit more testing to see what is causing it, it appears the problem relates to people being in the vehicle to be dropped, even setting the vehicles to be indestructible didn't fix the problem. The multiplayer code regarding collisions and the two vehicles seems to cause the problems.
ADVICE: if you are taking a vehicle in the chinook, get the the squad to board the Chinook and each paradrop out at the landing zone and allow the pilot to paradrop the vehicle and eject himself.
The squad then regroup on the ground and locate the dropped vehicle. This should avoid midair explosions.
Alternatively the squad can mount up in the vehicle but get the pilot to land the chinook away from the AO and unload the vehicle on the ground.