I had an older Blackburn Mag Trackstand (older than yours) and the resistance unit failed. Somehow the magnets were physically rubbing each other, and when your rode it, it would give off an odor like vaporizing metal. I pulled it apart a few times and never could fix it. It worked fine on the zero resistance setting though. I now use a Cycleop Fluid Trainer, and you can sprint out of the saddle on it. But always the rear QR gets stuck in the left axle clamp and makes it hard to get the bike off the trainer. I'm using the QR that came with the trainer.