I have a family member that has water in the directional (lense) of a 2000 Ford 150 van, wondering if anyone knows the source of the leak or is this even common?

Thank you for any assistance!

 

The front clear or yellow colored lens is heat sealed to the rear plastic reflector, and over time the seal will crack, allowing water in. Also, there is a little vent in the rear of the reflector, and if that gets plugged, condensation can build up inside.