Moin Moin! I’ve read more often here that some problems with blind rear lights have. After thousands of attempts to fix this problem also with my lights I have found the ultimate solution. Attention ! Fingernail care oil ! Yes , you have read correctly fingernail care oil . Do not ask how I came up with it, main thing it works . Fa. Essence Nail&cuticle oil (Drogeriemarkt Müller ). Apply slightly rub , finish as new . Greeting Uwe :