When you're in the "Hermit Gunsmith" room, after getting the items, it starts by trying to resume the "A CYBER's WORLD" remix, but then stops. Not sure if you meant it to resume fully, or if you didn't want it resuming at all until you go back out into the first cave.
The door in the first cave doesn't have a background doorframe. When you go through, it's just blankness. Same thing with the Mimiga Village/Cyber World door that leads to the Assembly Hall, and the door that leads back out.
When coming into the cyber version of the shack before there's any sort of Balrog fight, I notice that there's no door there. But when I go through the doorframe back out to the cyber mimiga village, a "door open" sound plays.
When falling into the Cyber World transformed Mimiga village, Quote falls twice for some reason. First, he falls off to the side, then afterward he falls like normal in the cutscene.
I thought that was pretty funny how when coming out of the reservoir, Toroko knocks King off the edge, and then if you talk to him it does the whole "god mimiga" thing. However, it would probably be good if you set a flag so that if you interact with that NPC again, the text box will show something more brief, because the weird Lancer expression and jingle gets old after the first time.
After King fell to the floor, I went into the save room, and came back out, and he was back up on the platform at the top instead of lying unconscious by the door to Arthur's house. Was this on purpose?
When I shot Toroko in the shack, and tried to leave the room without interacting with her, it said "It won't open!" Kind of weird that the door that isn't there won't open.
In Arthur's House, there's a stray tile from PrtCave:
I tried to enter the "Ma Pignon" room in the Graveyard, but then I got some garbled error and the game crashed.
Also, it might make sense to scoot the beds over one tile to the right, so that the bed on the left isn't cut off.
The "Save Point" in the cyberfied Egg Corridor could use a bit of work. First off, neither of the doors leading back out make the music start playing again when you get back out. The lower door doesn't have a frame behind it, and the places that you transition to when transitioning into the save room are off.
The door from the cyberfied egg corridor to Egg No. 00 doesn't have a doorframe behind it.
And the open doorframe from the cyberfied egg corridor to the "Side room" disappears when I enter through it.
When returning from the cyberfied egg corridor, "Mimiga Village" is playing instead of "A CYBER'S WORLD" when returning to find Sue in the cage.