I had a problem with excess vibrations on my
UDM at speed 6. It was almost impossible to hold it one handed. Check and make sure that the spindle is exactly perpendicular to the machine. If a pad seems to make a figure eight pattern while looking at it from the side, then I would say you have a defective machine and turn it in for warranty service. They do a good job ( the perfect shine) of taking care of any issues promptly.