Revealing mistake: At the end, when the Colonel is at his control panel on the phone just after the nuke goes off, the cord from the phone begins to peel from the control panel. This is mentioned in the DVD commentary.
Revealing mistake: When Trash slowly rises in the rain storm because she is now a zombie, she is noticeably wearing flesh colored shorts.
Revealing mistake: When Ernie catches the zombie eating the paramedic, the paramedic is obviously a rubber doll as indicated by its jiggling fingers.
Revealing mistake: As zombie Freddy breaks down the door of the chapel, where he has been locked in, he rolls over a bench which is barricading the door. As he lays flat on the ground, about to get up, his shirt lifts up and you can see that not all of his stomach has been painted with "zombie skin color". (01:10:00)
Revealing mistake: When the guys are putting the bench in front of the door to keep Freddy inside the Chapel, the bench lands on Ernie's foot and breaks it. The bench never even touches his foot.