This has been something I've been noticing with some of my unlicensed games. One of my generic copies of Digimon 3 Crystal runs on all GBC system, except for one of them. It has trouble running on my teal system (after the boot screen, it fades to white and just stays there) but it doesn't on my Violet or Pokemon Yellow GBC system. It also runs fine on my GBP and GBA, just not that lone system. I know the thing's not broken because it plays my other games just fine, it's just this one game it has trouble with, and the game has no problems on any of my other Game Boy systems...
To throw another example out, my generic copy of Thunder Blast Man wouldn't boot on a GBC when I first got it, but just fine on everything else. Now, it magically works on my GBC systems. If I went through my other games, I'm sure I'd find more examples. I would think it's oddly-specific copy protection (perhaps a short-lived revision?) but I only encounter this with generic unlicensed games, and it happens on the same generation system too, so it's not like it's just a compatability issue with that particular generation.
What I'm asking here is, what could be causing this?
