Konami Advantage + Serial IO Error

[PBR Pissburgers]

Afternoon everyone. I seem to be posting into the abyss here, but I am working on my Konami Advantage +, and absolutely everything is working on it. Every button, the touchscreen, reels, handle, all works. I just can't get rid of this serial IO error. I have replaced the small board on the back of the machine which the manual calls the reel, LCD, and handle PCB. I have reseated every connection to the backplane, replaced the batteries on the MPU, reseated everything going to the touch screen, and RAM cleared it a bunch of times, trying different settings. Still have the serial IO error.

It is error 190, which the manual says to check the harness going to the main door and the control panel, and it is under the touch screen section. Looking at the wiring diagram I see an SIO CLK, SIO OE1, SIO DOUT, SIO DIN that goes to the WIN & CREDIT LED PCB, as well as the reel, LED and handle PCB. Is the lack of signal on these wires what is causing my errors? Where do I go from here? I suppose I could try to replace thee WIN and Credit PCB? Is my MPU just bad?

Any help is appreciated!

[PBR Pissburgers]

It's me again. I have fixed the problem! Turns out my hunch was correct about the SIO CLK, SIO OE1, SIO DOUT, SIO DIN circuit. Replacing the WIN & CREDIT LED PCB fixed the error.