Compaq Portable II fails to boot - some analysis

Sometime ago I posted a request for help on my two Compaq Portable IIs that failed to boot from the FDD. I now can boot one using an "off the shelf" (at Weird Stuff) half height 360 kB FDD in place of either of the two Canon 5201 1/3 height FDDs that were in the two Portable IIs. Both exhibit the same failure mode, while trying to read the disk visibly spins erratically, as if there were some form of stiction causing it to go slower and then faster. Manually turning it with and without a disk, the spindle motor feels free of stiction. It is surprising to me to find both Canon 1/3 height FDDs fail in the same mode, suggesting a fundamental flaw in the design. For example, the full height and half heights I used in this project are older than the Canon's, of unknown provenance, but all 5 have worked flawlessly. Any ideas, other than avoid old Canon 1/3 height FDs? Anyone have a working 1/3 height 360 kB Canon FD? (I think I need Canon to get the bezel right on the machine I am "restoring"). Tom PS: I bought a package of 20 360 kB FDs off the internet and one of my problems was that about 1/2 of them were full of defects, causing some of my problems. I finally solved that problem by throwing away any disk with any defect found during Format and doing a Diskcomp after each Diskcopy.