They turned Soul Music into Soul Music, ruining it in the process.
Amongst the wonderful Quotes from the book was a great parody of the Blues Brothers. In this paritcular version, they LEFT THE SCENE OUT ENTIRELY.
I must explain that Soul Music is probably my all-time favorite Terry Pratchett book. I can probably quote the entire scene from memory. I know I recited it to Chichi. It always makes me laugh. I expected that scene, I wanted it to be done accurately to convey the full humor. Instead, it was removed and somethign completely unfunny was put in its place.
There were other ruined scenes, but that one is what made me stop watching.