Lock the driver into his seat

[michaelpatriot 10]

Hi, I'm making a mission where my squad needs to meet up with a convoy after arriving by heli. This convoy is a HMG humvee, transport full of troops, and a normal humvee. They get into the normal humvee and go to the enemy base, but I'm having seemingly unfixable issues. First my squad only gets in the humvee half the time, I can't figure out why, they have a "get in" command right on it. Second the driver for the transport keeps getting out then the other two take off without the 14 troops in the transport arriving at the base very shorthanded. Sometimes he will get back in and everything will go smoothly but he shouldn't be getting out at all. Can I lock the driver to his seat where he can't get out? Also can I make certain my squad gets in every time or is this just a glitch?