Hi Joe!
I worked during a few years in commercial A/C and I think I might help you understand what is going on.
Not sure though if I will have the solution because i don't have one yet.
I need you to answer a few questions:
In which conditions does this happen?
Anytime of the year or just under specific weather conditions?
Does it happen when the vehicle is under bright sunshine and/or even when it is inside a garage?
Also need to know if it happens after using the car's A/C or if it occurs at any moment?
You said other cars in the Family suffer from the same.
It happens on all the cars at generically the same periods?
Tone