Sorry, I figured it out. I'm an idiot. I didn't have a manner.txt in my custom grf and added one but I named it "manner.txt" but, instead of it saving it as a txt, it set the name as that. So the file name, including extension, was "manner.txt.txt" and so, as a result, the game resorted to the data.grf's manner.txt. I fixed the name and now it works properly. Thanks for trying to help me, unfortunately it was something so small.
