Did you test them in all ways?
I'll receive soon a Super Famicom and I'll see if PAL one was my problem.
Remember, Chrono Trigger hangs, Rudora no Hihou hangs, Seiken Densetsu 3 when arriving a specific point restarts again at the map (or something like that), and ToP runs cool :)
But now again... Mario Kart(the original cart) if is loaded from up the SWC DX2 then has GFX glicths at the start of a race... you need do a reset, then it works perfectly... why? I don't have the answer right now, but I really want it :)
And of course, I only can say it about my own experiences, and bahamut and someone more said the same about square games... dunno if your copier is from stock or just newer... but I don't think in coincidences, just in facts. And it's a fact my SWC DX2 64 doesn't work properly.
Regards