CPS1 layer/object error

[tiff_lee]

Ok so i've got an Aliexpress special Knights of the Round conversion with a small graphical fault.

Everything seems to be working fine with the exception of,

• The first boot screen text showing game/revision/region does not disappear on the second screen it remains in the form of red garbage
• During attract mode it comes up insert coin fine but when the text should be off/invisible it becomes red garbage instead
• The score rankings table is in front of the brick wall surround when it should be behind it

From what i've read the way CPS1 works with layers, so if I'm understanding it correctly the artefacts i'm seeing are items which should be behind another layer?

I've swapped to another working A board, fault remains.
Removed all eproms, cleaned the pins as they were very oxidised/grotty, fault still remains.

I'm guessing next step is to verify contents of the eproms? does anyone know from experience what area I should be focusing on?

cheers, Lee