What is wrong with my Zero Wing PCB?

[Steven]

Basically I was given a Zero Wing PCB with graphical glitching in exchange for some manual labour. I knew it was glitched before it was given to me, so no, I didn't get ripped off or anything like that. Basically the game is mostly fine, as the only thing that it does is make the stage 1 boss look like this

Spoiler

And then when you break his part he looks like this

Spoiler

Yep, you end up fighting just a jaw.

The glitch doesn't impact gameplay at all, unless you are me and find the glitch absolutely hilarious to the point where I can't stop laughing, resulting in me having difficulty fighting the boss properly.

Obviously this shouldn't be this way, but I am wondering if there is anything I should be worried about.

[Sumez]

Nothing to worry about, unless you have an actually leaking capacitor on the PCB, which would require you to replace and clean immediately.
If there's nothing visibly wrong with the PCB, there's hardly any risk of additional damage.

This looks to me like it could be something like a faulty RAM chip where the graphics data is held (sprites/bg layer?). Though, does it happen in other similar places, or is it only that one boss? If it's the latter it could be something as simple as an EPROM replacement (I'd try taking out every EPROM, dumping them with a cheap writer, and checking against romident, to see if they match MAME's checksum list).

Also very likely it could be any of the smaller ICs that handle mapping out addresses for the various RAM and ROM chips. Hard to know exactly where the fault is without a logic probe.

[Steven]

The PCB looks immaculate. As far as I have seen it's just this one boss, although apparently the stage 7 boss might be affected as well. My Astro's monitor is in the vertical position and I don't really want to rotate it just to play Zero Wing since that thing is fucking heavy, but I guess I can turn on the invulnerability DIP switch and check the rest of the stages in vertical mode.

I do really want to play the game, though... should have gotten a table machine instead of the Astro, I think.

[Steven]

A year and a half or so of doing absolutely nothing about this and I have finally found someone who might be able to fix it. Hopefully it can be fixed, but I'll find out eventually.

Since I am having trouble sleeping again and can now record from PCBs (with borrowed equipment that isn't mine) I can finally show what this looks like properly: https://youtu.be/VcNISi-pWOw

It gets a little more weird if you destroy the top part, which makes just the lower jaw remain.

I have been told that the stage 7 boss also has something wrong with it on this PCB, but I haven't seen it for myself.