Might be a stupid question? But why are you replacing the rear brake bulb?

Originally on our X5 we thought the bulb was dead (OBC informed us of that) and it could be seen from the outside. New light didn't help, it turned out that the light fixture had melted and was shorting..!

Interestingly enough this was on our 04 X5, our 02's lights never had a problem whatsoever...