SFZ2 Graphic issue

Newbie here seeking advice, I picked up a cheap sfz2 from market place to hang on the wall. I assumed it was dead but decided to check the battery and…3.6v.

So I ordered a cheap supergun and it fired up no worries, but had graphical issues.

I de-cased and made sure connections were good, cleaned both boards, reseated all the roms but no luck.

Any suggestions on what I should check next?

I am a newbie too but on MVS, I have used emulators to help diagnose by corrupting the EPROM one by one and launching the ROM in emulator until finding which one gives me similar glitch on PC when corrupted, to help spot the faulty one. If that helps.

Update: done some tracing and found pin 72 on CGD and pin 8 on RA33 had a break. Bridged the 2 together and problem solved.

Unfortunately I then changed the battery and got a white screen haha

Good job! Nothing an infinikey can't solve I presume?