Revealing mistake: When Jack punches the old lady, he swings way off target, and also 'she' (the stuntwoman, really) turns towards the counter and uses her arms to push herself to the other side. (00:04:45)
Revealing mistake: When he old lady jumps over the counter to attack Jack with a cleaver, she is replaced for the physical struggle by a younger person; you can see her face when the two struggle against the table. (00:04:55)
Revealing mistake: Jack just killed the first Trancer of the movie; the special effect of the corpse disappearing is not only visually poor to the point of being obviously fake, but it also has a clear mistake in execution; there's a spoon on the kitchen counter that changes position between frames (someone on set was careless and moved it, ruining the composite shot). (00:05:25)
Revealing mistake: Jack just killed the trancer old lady at the diner's. The place was empty and nobody else was supposed to be there, but as he turns away from the charred remains, in the top right corner of the frame you can see someone peek as Tim Thomerson loudly stumbles into the kitchenware on the floor, and then nonchalantly get back to their business. (00:05:40)
Revealing mistake: When the policemen are looking for Jack who poses as a hobo, and when Lopez confronts him and gets killed, the scene is supposed to happen to during the night, but what appears to be daylight comes through the openings (we see the outside of the building when they all escape and there's no light source like that). (00:53:15)
