1 of 2 bulbs in upper unit stopped working. I replaced the bulb 10W, 12v & both bulbs worked. Later, both bulbs stopped working. Both bulbs have continuity. New bulbs don't fix issue. Ideas??

1) Turn off power to the unit
2) Open the lower oven door
3) Remove the side trim screws and pull the trims down and out.
4) Remove 2 screws on the sides of the control panel.
5) Open the Microwave door. Remove the 3 screws on the Air Vent Plastic Cover on top of the microwave. You can then remove the Air Vent Cover by pushing the control panel up and pull out slightly at the bottom.
6) Remove the 4 screws on the Air Vent Plastic Cover on top of the lower oven and remove the Air Vent Cover. (You may have to remove the left under side bracket of the Microwave door temporarily just for the Air Vent Cover to clear the screw of the bracket. Re-secure the side bracket of the Microwave door panel as the front panel may fall)
7) Remove the 2 screws which held the Microwave unit in place behind the Air Vent Cover on step 6.
8) Wiggle the Microwave unit out about half way to expose the light bulb unit on top center
9) Wiring to the Control Panel will prevent you from pulling the Microwave unit out any further. And you don't want to do that as the unit may fall. Space is cramped, but working carefully with your fingers or pliers you should be able to release the springs which held down the light bulb unit and change the bulb.