I've just started with the game and I'm having a blast with it. It takes me back to my early teen years playing Defenders of Oasis, hehehe.
By the way, what I'm going to say cannot be considered a bug, but rather a warning to other players. I'm playing the game in Windows 7 with the Genesis Plus GX 1.7.4 f64e755 core of retroarch. I'm having lots of glitching problems when using savestates and loading from them (the graphics often glitch, specially inside of caves. When that happens, it's dangerous because you can walk through walls and end up stuck inside of solid rock and unable to move). I'm sorry if the explanation is not very clear, I'll try to record a video showing when this happens.
I've only tried this emulator, so I don't know if this also happens in every emulator with savestate feature included. So, be very careful when using them. Have always more than one savestate (or avoid using them except in cases of extreme necessity) and also use regularly the in-game save feature to avoid getting stuck in the game.