tokoro

How can I avoid this they are new and very expensive
Is theres any product that I can use to stop this??

Silvertarga

run a bead of clear silicone sealer at the point where the lens meets the body of the unit, also make sure you have the little foam seals on the bulb socket or silicone seal them as well

Lenses are notorious for separating from body

HiWind

there are breather hoses that shd be attached from the centre rear light to each of the side lights
they are clear plastic and shd help with condensation (i think) so check yours are attached.

HiWind

Also it seems light design changed in 91 to help prevent this ...