I had the same problem on the passengers side..examined the cover
and found a very tiny crack caused by a stone, gave it the hair dryer treatment
on not very hot as you dont want to damage the plastic cover, when all the moisture
had evaporated, I just sealed the crack with a tiny drop of superglue, end of consendation.
This also worked on my S500 glass headlights when I got a stone chip on one. :thumbs: