It has to be either a diode or a short. I don't have specific suggestions I'm afraid, except to keep gathering data until you puzzle it out. I had two rows in another game shorted together and it turned out a blob of molten solder had landed on a connector, shorting the pins together. I found it by unplugging various harnesses. Is it at the board? At the lamp? Elsewhere? And so on. Here's what my notes looked like after a couple of hours hunting. Good luck!