The two metal brackets that the cone rests on can come out. They could be cleaned with a wire brush attachment on your bench grinder. Or you can buy new ones they are cheap. you can also buy a guide template to adjust the setting of your sitter.
Do you know a potter or teacher in your area who can show you? Not complicated, but I am a two finger typer and this would take a lot of words. Better to show.
I think I can speak for the rest of us, when we assume all Canadians are polite. I for one, poke fun at the notion. A stereotype, does not define a nation. Though, all things considered, that's not a bad one to have. When people think of the U.S., they think we are overweight, gun-toting bullies.
I've heard enough of your classroom stories, to know, that there are quite a few Canadians, that are far from polite. I of course, can relate. I also work with the same clientele you do.