Continuity mistake: When Stallone and Williams are on the back of the train, Stallone smashes the window. Cut to Hauer. After this, the window is shown again, and the hole in it is larger than it was when broken.
Revealing mistake: All of the bullet holes in the target Da Silva fires at are wrong. When a bullet hits something, the explosive force exits in the same direction as the bullet, yet when you look at the target, you can see that the ruptured paper of the target has blown toward Da Silva, obviously a side result of having explosive charges on the back of the target to simulate bullets going through.GalahadFairlight