Muchi Muchi Pork PCB fixed itself?

[EOJ]

In mid-June I noticed (in a few credits) an apparent graphical glitch on the right side of one ship sprite in Stage 2, after the midboss. This sprite does not occur anywhere else in the game, and the whole section only lasts about 20 seconds. A very minor "glitch" IMO. Here is a video I took of it back then:

https://www.youtube.com/shorts/c4reiGaE8Xw

After noticing this apparent glitch I put the PCB away and I didn't play it again until today. Much to my shock (and delight) this glitch seems to have disappeared!! I played two credits to confirm, and both times it was nowhere to be seen. Here is a video I took today:

https://www.youtube.com/shorts/-y-GkM7s8t0

So how did this PCB fix itself? Some built-in Yagawa error-correction when rebooting the PCB and loading the EEPROM?

Anyway, I will put this up for sale here soon.

[EOJ]

I played 3 more credits. Still no sign of this previous glitch.

I've listed it for sale in the market forum at a discounted price, because I can't guarantee the glitch won't return. But I've tested it enough today to be satisfied that the glitch is not currently present.

EDIT: Tested 3 more credits, including one on the 2P side in case that made any difference. Still no glitch!

[EOJ]

I asked about this on the Arcade-Projects forum and received some helpful replies from buffi and rtw:

https://www.arcade-projects.com/threads/espgaluda-2-cv1000-repair-of-bad-u2-nand-using-jtag.19108/page-4#post-394352

Neither is sure exactly what happened in the case of my PCB, but they post some interesting possibilities.

[EOJ]

I did the TGA test in the extended test menu. It took awhile, but I found one frame of one sprite that was causing the previous issue. In frame 01E4=228, I found the glitch:



All the other frames of this sprite are fine, for example 01DA=218:



However, after doing this test I played again and still didn't see the glitch on the sprite in-game. Maybe the game is not loading that glitched frame, it's just skipping it? That's the only thing I can think of.

No other glitches were found in any other sprites, thankfully.