Rockman 4: Minus Infinity v1.0 bug

Hi, I recently bought a Famicom version of Bandit Kings of Ancient China and sent it over to Leon from nesreproductions.com to have it made into a Rockman 4 : MI cart. It seems to work well, however there is a graphical glitch I've found that occurs every time I encounter a boss on Cossack 2 or 3(I forget which one). This graphical glitch does not occur in nestopia or FCEUX.

Is this related to inaccurate MMC5 emulation? Or maybe the cart was miswired somehow? I found this a bit unlikely because everything else seems to work.

here's a clip of the bug in action :
http://www.hitbox.tv/video/403419

Thats 'normal'. Mine has it, and there are a couple of other small graphical glitches but nothing game breaking. Its common that extensive hacks have a few graphic screw ups here because if it works on an emulator, its not 100% guaranteed to be perfect on the console. Some are major, some are minor. This one is minor.