Revealing mistake: Towards the end of the movie, when Steve Austin is on fire during the fight, you can see it is a stunt man wearing a burn suit for a split second.
Revealing mistake: When the guards enter the room where Sandra is tied to the chair, she kicks her leg out to fight them off but when the chair is tipped over, we see her feet securely tied together. (01:10:44)
Revealing mistake: Just as Yang jumps from the black truck, Barney's truck can be seen doing a sharp turn in the warehouse. However if you look at the floor you will see skid marks from previous takes. (01:00:40)
Revealing mistake: When being chased by the military, there is a shot of the blue truck driving towards the camera down a street. In this shot, the tyre marks from previous takes can be seen on the ground. (00:38:00)
Revealing mistake: When the pirate leader holds his hand up looking at the laser sights following it, his palm is facing away from the expendables, but the red dot still appears on his palm. (00:04:50)
Revealing mistake: When Christmas is filming the army, you can see the switch on the camera is at the "Off" position. (00:29:30)
Revealing mistake: When Lee meets up with Lacy's boyfriend, Paul throws his basketball away just before Lee punches him for the first time. However, when Paul actually flies backwards, Lee's fist is nowhere to be seen. (00:49:05)
Answer: The intel they gathered on Church made them believe he would have killed them all upon completion of their mission.
Phaneron