The underwater light alternates between being on and off as Mac uses its broken face to cut himself free of the straitjacket.
When Roxy and MacGyver are clinging to the pipe in the elevator shaft after the elevator falls, they are approximately halfway between floors 7 and 8, but when they look down the shaft, floor 7 is shown about two floors beneath them as though looking from floor 9 or 10.
Elevators have safety brakes that clamp down on the guide-rails if the elevator starts to fall, so the elevator box would not have gone crashing to the basement just because its support-cables came loose.
There are too many mistakes in the elevator scene to list. First, it's not that easy to get to the car top. Unless they are in a seismic zone, it shouldn't be possible to get out of the car through the car top exit - and then only with a key.
Like someone else noted, the elevator safeties would've stopped it from crashing into the pit.
When MacGyver opened the hoistway door at the penthouse, it would've been easier to use the pick-up rollers to open the door. Then, the door wouldn't have stayed open, it would've closed so not to leave an opening to the hoistway.
The car top light should not have been on when MacGyver climbed out and the hoistway would've been very dark after the elevator crashed (which it wouldn't have).
When the elevator falls, the loose cables fall with it, despite having supposedly become detached from it, meaning they should remain hanging from the mechanism above. Also, later in the elevator shaft scene, the view up to the top of the shaft shows no mechanism, no cables, and no aperture for cables.
The two dangling curled ends of the loose support-cables visibly "jump" to a less "still swinging" position just before Mac's head appears above the top of the elevator box, indicating that a few seconds of footage were cut out there.
Rogan was on the balcony, leaning on the railing, reading through a file of papers, when Carla, disguised as Roxy grabbed him by the leg and threw him over the edge. He fell to his death. But when he went over the railing there were no papers. And in the next view from the ground as the man is seen falling, there should have been a flutter of sheets of paper floating down.
When the manager was thrown off the terrace he had a file of papers in his hand. They did not seem to go over the side with him.
In one of the scenes where MacGyver meets Roxie at her penthouse apartment, a good portion of a boom mic is clearly visible in one of the large mirrors located in Roxie's living room.
For some reason after the elevator crashed nobody, whether it was people in the building or the management staff, came to help or go to her apartment to see if she were okay.