Audio problem: When Jesse and Ron are doing press-ups on the sports field, Ron says "So what about you and that rich babe you've been cruising to school with every day?" You can see that Ron starts to move his mouth a few seconds after the words are spoken, and his mouth doesn't move correctly to the words being spoken either. (00:10:30)
A Nightmare on Elm Street Part 2: Freddy's Revenge (1985)
1 audio problem - chronological order
Directed by: Jack Sholder
Starring: Robert Englund, Clu Gulager, Robert Rusler, Kim Myers, Mark Patton
Revealing mistake: When Jesse is cleaning out his room, he puts a tape into his tape player, and presses a button down on the top of it. But halfway though the scene of him packing his things away, you can clearly see the button is no longer pressed down, yet the tape still plays. (00:18:10 - 00:19:00)
Ron Grady: So, what about you and that rich babe you've been cruising to school with every day.
Jesse Walsh: What about her?
Ron Grady: Are you mounting her nightly or what?
Trivia: Take a close look at the bus driver at the beginning of the movie. It is Robert Englund without his Freddie makeup/costume.
Answer: I think the coach's death was a play on his character being at a S&M bar. People who frequent those places are usually into bondage and being dominated. Hence being tied up, and whipped with the towel. It also fits in with the homoerotic subtext throughout the movie.