When Frank Leone is quickly forced out of his tiny jail cell his pants are not on, but as he appears out of the cell his pants are on.
An electrical cable Dallas used to electrocute Officer Manly and himself changes position between shots after Dallas rips it from the circuit panel. It alternates between being attached to the railing and laying on the floor, completely detached from the railing.
When Leone (Stallone) is getting forcefully taken to Gateway Prison, he is shown getting cuffed while just wearing a sleeveless T-shirt. However, when he is getting taken outside to be transported, he is wearing another (prison?) shirt on top of that. With his hands cuffed, the guards would not have been able to have Leone put another shirt on because the cuffs would have got in the way.
The inmate that gets the wind knocked out of him by Eclipse during the football game hat flies off, but it miraculously appears back on his head.
The front glass on Leone's windshield gets broken twice after it reappears.
Normally, prisoners are not allowed to wear personal effects and jewelry on themselves in prison like Frank is with the chain and ring around his neck. It is possible the warden purposely let him wear it in prison because he knew it would make him a target for other prisoners as part of his sadistic vendetta against Leone.