I had an 8" drive do this same kind of thing. I really thought it was destroying the disks. Later, it became apparent that the brand new old stock disks I was using that I bought on eBay were bad disks. They were shedding magnetic material.

Now, before I use any disk in the drive, I use this cleaning device I bought on eBay (https://www.ebay.com/itm/303620862566 ) and clean the disk with denatured alcohol. This will remove any loose magnetic material from the disk. You can actually see the magnetic material come off on whatever you use to clean the disk with. I use these big cleaning swabs (https://www.amazon.com/gp/product/B085T2JJPT