Condensation inside your headlight means that water is penetrating somehow. This can even be water vapor or humid air that finds its way inside and condenses when cold. Water can penetrate through seal between glass and the whole assembly. If I recall correctly its not like an earlier 850/70 series - it uses a urethane caulk. The plastic portion of the assembly can be cracked. There are o-rings which seal the back covers (removed to change bulbs) to the assembly. Ever been in an accident? Sub OE quality parts can have just this type of problem.