I thought this was an interesting discovery if you're willing to sacrifice the media to recover some data. I've been trying to read some nasty old 360k 5" floppies circa early 80's, the kind that squeek and strip the oxide off in nice little rings. These were probably made from the same nasty stuff they made early 80's magtapes out of. Thinking this might be a dirt/lubrication issue, I tried applying whiteboard cleaner to the disk while still in its sleeve using a lint-free cloth across the slot on both sides, rotate, repeat around the whole disk, and after a few head cleanings was able to recover the data (and the squeeking stops). Weber Costello Markerboard Cleaner (from the label, after water) octylphenoxy polyethoxyethanol trisodium phosphate ethylene glycol monobutyl ether it's probably the glycol acting as a lubricant