Make sure you use Sylvania bulbs at all bulb locations. Remove all of the light bulbs and spray them with electronic cleaner. Remove all of the fuses and use an emory board to clean up the ends of the fuses. Then spray the fuse connectors with electronic cleaner and replace the light fuse (#6 on mine) with a NEW fuse just to be sure.

Past that it might be time to get out the multimeter and start running voltage tests.