Hi all. Last night I was playing and noticed the left slingshot wasn't working, everything else was fine. I turned off the pin, repaired the slingshot under the Playfield (opposite side of the opto board) and booted up and am getting this error now, and all 4 balls are sent to the subway. I replaced several fuses and tested the rest which did not solve the issue. I also replaced the chip in U20 (socketed) and that did not solve the issue either. The red light on the opto board under the Playfield is illuminated, but LED3 behind the backbox isn't (I've read somewhere it's not supposed to be). I also cleaned all optos with a q-tip.
I've been doing a bunch of searching and see that this is a fairly common issue, but the solutions seem to vary. Hoping to get some help from the Pinside community.
I've attached some pics for reference