That's incredibly helpful, and insightful. I hadn't thought about sanding/grinding/etc down the outer layer. Given the issues with the CD-ROM2 gear ... aging poorly ... I suspected that the D-Pads (or some batches of them) may have been manufactured from a plastic with different aging process or something. Heavily annoying problem - I take pretty good care of my stuff, and almost all of my retro hardware is mint/near-mint EXCEPT these couple of d-pads ..
Ah, the joys of retro gaming ...
Ah, the joys of retro gaming ...