That's my experience as well. The ones that fail are 3.5" HD floppies (1.44MB). Over on the ctech mailing list an old-timer expert explained that it's basically

That's my experience as well. The ones that fail are 3.5" HD floppies (1.44MB). Over on the ctech mailing list an old-timer expert explained that it's basically because the 3.5" HD floppies are just above the density limit the medium and technology can handle, which is why the 720KB DD floppies are fine (and 1.2MB 5.25" ones are also fine), but the HD ones fail. I tried to recover all my floppies from the eighties and nineties, it went very well except for the 3.5" HD ones - couldn't recover a single one, whatever drives I used. From what I'm told the 8" ones should read fine too, we'll see.. I have many, and I have a drive, but I haven't got it set up yet.