Nope, I don’t think so! I’m using a cable from Retro Access’ eBay store, prior to the new site they have. Their other cables have left me happy. In fact, I actually have two SNES cables from them (1 CSYNC, 1 standard) and both of them show the same problem on both consoles. Hmmm.
Tried again with my Saturn And Genesis and they seem fine. No weird sync skips. I’ll try a couple of additional tests and see what I can come up with.