Simple, DYOM needs External scripts in it. Things like parachuting usually fails because it's a external script (as you already may know) and some other things like poker maybe I dunno. In the next version, add them, because they're necessary for some missions people have made.
A bug - When you end a mission while the player is in a vehicle, the game will crash (unconfirmed). Put in the mission ending a check if the player is in a vehicle then remove him from it then continue the rest of the mission ending stuff.