Did you disconnect the switch matrix connectors on the MPU to determine if the problem is on-board or off-board?

Edit: just confirming the= 8 + )

I tried annotating the switch layout to highlight rows 5, 7, and 8 to see if they have anything in common.

I didn't find much.

The Eddy boards for "Hit Red" and "Hit Bulldozer" are on row 7.
The Eddy board for "Hit Ted" is on row 8.
The bulldozer opto board uses rows 2 and 5.
The 7-opto board uses rows 1-6.

Is this a board problem?

roadshow_(resized).png

When I had a Road Show, I remember once upon a time accidentally discovering that the 'Start City' kickout scoop was shorted to a coil log and was hot at 50V.

I think the blast zone or scoop kickout have to be your main suspects here. There's just a lot of targets and a lot of metal under the playfield there.