I'm not sure if this correlates to the common dim odometer display problems that earlier Expeditions/F-150s had. Here's a thread that details that problem including an easy fix. I did this fix when I had my old 99 Expedition and it worked perfectly. I've had no problems with my 07, but you may want to look into is a possible cause.
https://www.ford-trucks.com/forums/1...lem-fixed.html