Hm. These two disks are now 100%. I have just re-captured both of them and they went through first time. The sector on the original capture was miles out, 2us for example. I was having some trouble with the Logic device, complaining about not being able to capture at a certain rate.
So a couple of things; maybe Logic was messing me about, or a couple more spins have shifted the dirt from the disk surface (they were both very dirty indeed).
It’s probably a good idea to get myself a drive head cleaning disk and maybe clean the drive every 20 or so disks that go in it? Anyway we’re up at 50/50 so maybe tomorrow I’ll scan some more.