When one of Dahmer's victims can't start his car, he talks of a dead battery but the starter of the car worked perfectly so the battery is charged. Dahmer offers to give a jump start although he could hear the working starter too. Dahmer is likely preying on his victim's lack of knowledge about cars to lure him back to his place.
When Dahmer's victim awakes from his overdose in the hospital, the bed and heart monitor were appropriate to the late 1990s, not the late 1980s as depicted.
The family of one of Dahmer's victims is playing a home video game system, but it is making the sounds of a coin-op arcade Asteroids machine, not the sounds of any 1980s home game console.