Thanks for playing!
Mirroring went through a series of working and then breaking and then working as time went on and I changed and added things, I'm not sure what your recommendation is but I feel like I had a decent grasp on priorities after I started using ZGB (I started over on this game 3 times, once with GB Studio and once with plain GBDK). My primary goal was to get to the point that the game was mechanically functioning, getting the graphical stuff in order was secondary
Have you tried the post-jam9 version/compo version on github with everything fixed(or did I misunderstand and you're talking about a different mirroring problem)?