The Genesis and NES portions may be enough to make the deal for me (depending on if Castlevania 3 is compatible). How bad is the counter-clockwise rotated SNES controller layout though (if you've tested it)? Would you say it is game-breaking, or is it operable with some getting used to?
Maybe the SMRPG cart is a bit dirty, or the pins are being finicky on the Retron3. I would assume the Retron3 uses the same SNES hardware as the Retro Twin. Also, it's curious as to how the sound is worse in the Retro Twin, which has less hardware than the Retron3. Perhaps it has the same innards as the Retro Duo?
Are the carts cleaned? Sometimes these clones' pins can be finicky. If the Retro Twin does have the same NOAC as the Retro Duo, or at least an updated one, then it should work. If Castlevania 3 truly doesn't work though, I may have to pass on this one...
All carts have been cleaned by us in the store, Retron 3 SNES hardware must be the same as the duo, the SMRPG game works on the retro twin but not on the duo or retron 3, tested 3 different castlevania 3 carts, they dont work on neither clone