Floppies don't seem to follow the rules.
When I got back into using Amigas a few years ago, I bought some NOS DD floppies, since that's what everyone recommends. About 7/10 wouldn't even format. These were brand new discs, still sealed, that had been on a surplus store shelf for 20 years.
A few months ago, I found a bunch of PC HD floppies in an e-waste bin, and almost every single one works perfectly on my Amiga. Every disk that managed to format properly has been completely error free.
