Reply by Grandpa

I had a sander do something like that once. It was a PC 505 pad sander. it would dart around and I was simply not big enough or strong enough to stop it from having a mind of its own. I finally resorted to the owners manual and it described my problem. the felt pad on that sander was not flat and it need to be cleaned up. I put a piece of sandpaper on a flat table (full sheet) and set the felt on the paper and started the sander. with the sander running I would pull it toward my body and it remove a bit of the felt pad. After a couple of times across the sanding sheet I put new paper on it and it worked like new. Maybe something like that??