There are several things that could cause the marker to come off one side but not the other. Take a closer look at the bevel and try to determine if it's making any contact at all. One side of the bevel might just be rounded over from years of neglect.

You can fix this with the Norton 4K, but it will require time and lots of patience.

If you can give us more specifics, we can try to offer better advice.

Josh