I have the same problem, but when I replaced the bulb, it still didn't work.
Then I noticed a burn mark on the old bulb contact strip. (Couldn't attach image).
Is this normal? The rest of the bulb looks ok.
Damn. I had the exact same issue and my bulb looks exactly like yours with the melted plastic around the contact. I didn't even had to buy new bulbs since the bulb itself is not burned out. Could have just freed the contact (wasted my money). Looks like another Ford flaw. (like the swollen lug nuts)
Anyways, I put in a new bulb and it's working again.
Edited by Lacienega, 18 July 2018 - 12:28 AM.