Revealing mistake: When Fireball takes off for the first time, if you look way above him at the top of the tower block behind him, you can see the shadow cast by the rig that is used to lift him up.
Revealing mistake: During the prison break at the beginning Richards grabs a guard and says "How about a lift?" You can tell it's a dummy.
Suggested correction: I've watched this scene many times and still cannot tell if it's a dummy.
Look at the guard's limbs.
What about them? Still, nothing that points to the guard being an obvious dummy.
If you look at the guard's limbs, they are completely stiff and barely move. If it was a real soldier that was being thrown, he would have been flailing his arms around and trying to free himself. It is most noticeable at 00:06:51 that the guard is a dummy.
Revealing mistake: In the Sub-Zero fight scene, Laughlin (the black man) is on his back and Sub-Zero is standing over him. When Sub-Zero tries to kill Laughlin by hitting him with the hockey stick, he rolls to his right. Sub-Zero pulls the stuck hockey stick from the ice and tries to hit Laughlin again, but he then rolls to his left. The stick is once again stuck in the ice, but to the left of the stick there is another divot in the ice, suggesting Sub-Zero struck on Laughlin's right side twice, but in fact it was only once. Sub-Zero tries to hit Laughlin a third time, but he rolls to his right for the final attempt.