I just wanted to log this for the future reference of someone else. I had a Data East/Sega Version 3 "Hook" and an entire row of lamps were lit (flashing) when they were not supposed to be. The affiliated transistor and pre-drive transistor on the CPU board were good. The issue ended up being a faulty diode on one of the lamp sockets in that affected row. Replaced the diode with a 1N4007 and everything works as it should now.