My Tengen Gauntlet cart is a buggy mess. I've opened it up and cleaned it, but it still won't play correctly. The title screen works great, and all of the sprites are flawless, but the levels are messed up beyond playability. You can't pick up keys, and you can walk through random walls. It's literally unplayable.
To be fair, I haven't ever tested it on NES hardware. I only have a Retron 3 at the moment and no real NES. Is Tengen Gauntlet known to not properly work on non-official hardware? Or is it known for the carts to be finnicky?