I know this is almost a decade old, but I have the same issue with my FH according to main dealer it’s the socket itself which may have melted and become unserviceable, they gave me a new one to fit, which I will have a go at and post it on here. Should it work,
Btw as per the original post the fuses are checked with multi meter several times 64 65 67 are defo all good they have good continuity in both blades
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