Missing/wrong background sprites in King Of Dragons, is possible to fix this C board?

[bubbly]

Hello

I'm having problems with a CPS 1 C board.
The game is The King of Dragons* (Japan 910805, B-Board 90629B-3) (info taken from mame)
I know think it's a problem with the C board because the exact same thing happens using it with CPS1 Multi and also the original pcb. Interestingly, other games like Final Fight or Cadillacs & Dinosaurs work fine with the same multi + "faulty" C board combination. When using a different C board I usually pair with my multi, the game works without any problem
As you can see I use the multi as a programmer for the C board (it has the battery attached), mainly because I don't have an Arduino board to do a proper de-suicide programming.

Any clues about what could I do to fix this C board, in case it's possible? Should I try to reprogram it using Arduino, openkey cps1 or it could be because a faulty B chip?

Things I've tried
- cleaning contacts
- re-flown B chip pins from 1 to 80 and cleaning
- visual inspection -> traces looks good

btw, this C board has been previously modified to allow non decrypted games but I reverted the modification. I don't know if the problem was present before.

A pic after reverting the modification but before reflowing

The symptoms.

 

[bubbly]

(edited to add extra details)

 

[ack]

Kinda looks like you didn't revert the mod right? I have some pics here of how I would normally revert

https://github.com/jwestfall69/openkey-cps1?tab=readme-ov-file#reverting-a-modified-c-board

 

[bubbly]

sorry for the late response
I had this on hold but resumed today
Thanks for the link.
The mod was already reverted (show in the attached picture). Just in case, I just re soldered it right now but I still get same artifacts.
Pins 45 - 47 were not cut.

 

[GoldenGlover]

Your B-21 is failing.