When the guards take Jason to a room to be sexually assaulted by Dracona, he stabs Dracona through the hand with a shiv, but it doesn't deter him, telling Jason he is going to hurt him and make him scream. In the very next scene, Jason appears unhurt and not traumatized in his cell and Dracona isn't wounded from the shiv going through his hand.
When John is approaching the hoodlums that are terrorizing his wife in the parking cellar, he is seen with glasses in some scenes, but without glasses in other scenes, making the glasses appear and disappear between cuts.
When Jason stabs Darcona with the shiv, he stumbles back with the shiv in his hand. However, in the next shot, the shiv is embedded in Darcona's hand.
When Darcona (played by Sven-Ole Thorsen) is dragged out from a prison fight, it is clear to see that it is not actually Sven-Ole Thorsen himself that is being dragged out by the guards, but some stand-in guy instead.