I have an Axner electric wheel. It's 15 years old, but I've only really used it in the last 2 months. It began making a whirring noise today. Followed troubleshooting guide that came with model and discerned that when wheel is on and in neutral, if I turn it by hand there is no noise. Troubleshooting guide suggests greasing bearings but provides no guidance on how to do this. Can anyone point me to a video or instructions?