During the sequence where Ava is having her brain scanned by McCarthy's cranial rig, she decides she's had enough and removes it. The camera switches from a face-to-face where she is no longer wearing the device, to a profile view where she is wearing it, then back to the previous view where once more the device is no longer on her head.
After cutting the material off the machine version of Ava, the plastic snaps and the actress's eyes flutter.
Close to the end of the film, Machine is shot by the soldiers at close range, but her clothes show no signs of stress or bullet holes.
Towards the end when the robot is about to enter a dark hallway she speaks and you can see her breath in the cool air.
As Vincent cuts the covering off Machine's face and pulls it apart, a nostril hole that allowed the actress to breathe becomes visible.
During the test of the brain implant, Vincent asks Paul what cup Lucy "should" look under for the ball, and Paul replies "B, of course." Vincent tells Paul that that is wrong, because Lucy was out of the room when they switched cups. But the question was not which cup "will" Lucy look under, it is "Should", so Paul's answer is correct.