http://www.pinrepair.com/sys1/#lamp

Do you have a schematic? It looks like you probably have 2 groups of 4 lamps that don't work. I would think it is connector related (everything with my Count-down seemed to be connector related) and would "safely wiggle" some of the suspect wires. From the pinrepair site

"Four Lamps Don't Work.
From the table above you can see that any 74175 chip on the driver board controls four lamps. It's easy to suspect one of the 74175 chips as bad, but that's usually not the case in my experience. A far bigger thing to suspect is the connector coming from the bottom edge of the CPU board to the top edge of the driver board. Battery corrosion and age often takes its toll on these connectors, and the lamp signal gets lost from from the CPU board's spider chip to the 74175 driver board chip. Also on the CPU board the z24 or z25 (7404) inverter chip likes to die too."

You can get a new Driver board to MPU connector on eBay (or re-pin yours). I did and most of my problems went away after that. My game (Count-down) would behave great and then do something weird like this.