Have you looked over every inch of the bad board? Look for solder bridges, a stray piece of metal shorting something it shouldn’t, a broken fuse holder with one side flipped towards the one next to it shorting out.....
How did you check the diodes and transistors? If you have a coil locking on I’d suspect a bad TIP36. Not sure which one on a LW3 but I’m finishing up two of these boards for other data east games. Each had bad TIP36 devices. Most of the time a diode check on the meter can help weed out bad parts. It’s not perfect though. Any parts that I even suspect as being bad I’ll pull and use a transistor checker to compare against a known good part. You can get some decent ones on eBay for under $30.