Is the old padding dried out and stuck like concrete on the floor which I'm guessing beings it was finished hardwood. Something about the pad and the finish on the hardwood didn't like itself.
I had one where I was using a mechanical scrapper and it just slid across the top of the pad. Out of frustration I hauled off and smacked the floor with my hammer and it all broke off the varnish and then just basically swept it up. I honestly don't know what will happen with the diamond brush. We always just scraped it off with a wallpaper scraper, but wasn't worried about the hardwood as we were recarpeting it.