After Rickie gets hit by JT, the split on his lower lip keeps erratically changing shape, consistency and placement for the rest of the movie.
When we see Wheeler raping the Deadgirl, he finishes up and begins pulling up his pants while JT and Ricky are talking (seen in the background). When the camera comes back to Wheeler after being on JT and Ricky, he is still in the process and finishes shortly after that.
In the scene where Johnny & Dwyer see the body, the three scratches on JT's face change length, orientation, the side of his face that they are on.
After the bullies beat up Wheeler and Rickie in the asylum, we see Wheeler outside Deadgirl's room apologizing to Rickie and his face is clean. After they go into the room, Wheeler's face is once again covered in blood.
Joann was wearing a t-shirt and shorts when she died but in last shot, she was shown in a white dress. It is obvious that Rickie changed her clothes.
Before entering the abandoned mental asylum, there is a sign on a chain link fence that says "Hospital Employes Only"...the word Employees only has one E at the end, when in fact the word "Employees" is spelled with two E's at the end.
The dog cannot be in the deadgirl's room because Rickie and JT found that room on another story via a tunnel, while avoiding that dog in the first place.
There was no source of food and water for that dog is shown, but still he was shown strong and fit.