I'm not sure if this is allowed, but this is what me and my Squad had done.
Step 1: We finished the beginning with doing everything silent (Not sure if this is needed)
Step 2: Kill everybody you see until you see the soilder get snipped in the head and you're told to get into the humvee
Step 3: DO NOT SHOOT ANY BULLETS. For some reason the game glitches up.
Step 4: Do not shoot until you and your friend, random person or squadmate escapes from the burning humvee and than you're able to kill anybody you come across.
Step 5: Profit, the mission should play smoothly and the helicopter should spawn and such,
Possible bad TIP: Have the person who planted the C-4 not pick up the sniper (SKS), but the person who doesn't come out of the car. The guns would reset if the person had the C-4. Therefore gaining two of the SKS. (I'm not sure of this, but yes.)