As Mechanized Infantry using AI in the player's group, where the AI would play the role of the infantry that boards and disembarks the IFV/APC multiple times, if the player is in Gunner or Commander position, ask the infantry to get in the vehicle without move the vehicle since its spawn, the infantry will get in. But as the vehicle moves the infantry is not able to get in anymore, staying "stuck" in a specific point out of the vehicle's rear.

The only way to make the AI get in the vehicle after the vehicle changes its position is for the Player to change their seat to the driver one OR ask those units stuck to "STOP" and then immediately get in the vehicle.