Puzzle de Pon character glitch

[Ryoandr]

I got a Puzzle de Pon that was not working reliably, I think it just needed a good cleanup, as after it works every time.
However I noticed that if I move and stop in certain positions, part of the MC sprite would disappear, if I shoot without moving it would reappear.
I tested on 2 MVS models (MV1FT, MV1A) to be sure as I've seen some minor glitch appear only on some boards, but here it happened on both.
Also, I think it's a bootleg / convert / repurposed as it had aof C roms still on it and the boards don't match the ones on mvs-scans. The label looks genuine.
I checked in emus and some IRL footage and it doesn't seem to happen.

 

[Kujako]

So, good news and bad. Bad news is that it looks like you have a conversion/bootleg. The few mask ROMs on the boards are marked "044" which is Art of Fighting.
Compare with the legit Puzzle De Pon boards: https://www.mvs-scans.com/index.php/Puzzle_de_Pon!
Good news is that the issue is most likely down to data being corrupt because the EPROMs don't have their UV window protected. But, not sure which one. Looking closer it seems that the C1 and C2 are mask ROMs but not Art of Fighting. That's where I would expect the character sprites.

 

[Ryoandr]

Upon closer look C1 C2 are write-once EPROMs. The wierd thing is the data is there if I shoot as the character reppears, non buggy or glitched. Out of curiosity I changed the waitstate resistor as some games apparently use it to time graphics, but it didn't change anything.
All the UV EPROMs are unrelated to graphics (S1 excepted, but fix gfx are fine so...), Unibios CRC checks fine. It also happens on stock bios, and 2p is affected too.
I am pretty sure it's an official repurposed like the many Puzzle Bobble around, that many think are bootlegs.

View: https://youtu.be/jP6DWrvoMco

 

[Kujako]

I am pretty sure it's an official repurposed like the many Puzzle Bobble around, that many think are bootlegs.

It definitely doesn't look like an official conversion. But it is likely to be an unofficial one an arcade owner made when they didn't want to pay for a new game. UniBIOS CRC check is only looking at P1. You'd have to pull the C1&2 to check their contents. But not sure where the actual issue is. Depending on what you're setup to do, I'd check the C ROMs and continue on from there.

 

[Ryoandr]

I fixed it. I think I understand now :
it is probably a bootleg, and the maker didn't have 8mb EPROMs. PdP is a very small game and looking at C ROMs there's very little data past 4mb, most of it is FF. So they just went ahead and chopped the roms. I'm amazed there wasn't more glitches !
I used 8mb roms and no more glitches. I should have immediately checked EPROM size vs ROM size, but I was too candid and didn't expect someone could be so reckless

Thank you for the help and suggestions all !

View: https://youtu.be/Olk8QQmAtww