Something I noticed while playing one of my original discs is the appearance of granulated bars on the screen (barely noticeable). These bars don't appear when playing hucards. Could it be a power issue?
Whatever you're talking about here it has nothing to do with CDRs.
I'd say the laser is just getting old in your Duo or its settings are drifting. Since CDRs didn't exist back in 1988 the lasers in these units were never designed to read them. Many people have problems, many people have no problems. You get lucky sometimes but you can't expect them to work at all, honestly.
I've owned 3 PCE systems, currently 2, and they all read CDR with no issues, but its not that often that I actually use them since I prefer originals.