2007 Ford Explorer brake noise

I had my brakes 100% completely redone at the Ford dealer about 4 weeks ago, they tell me every part has been greased, looked at, working, etc. But I am and have been hearing for probably 6 months a horrible quick noise on slow braking only periodically after car has been sitting for awhile ie. In garage at night, at a parking lot at store, etc. And increased when it's cold outside or wet. I have been told this is moisture build-up on the 4 wheel disc brakes and it is common noise for 4 wheel disc brakes. If so, a common noise, then how come the first 1.5 years I owned the car I never never heard that sound and then it started and continues? I have taken it back to Ford over and over and that is what they continually tell me, it's common, it's moisture.
It does not vibrate or pull when stopping, it's only when slowly stopping such as coming out of the garage after sitting all night.
Any other ideas or is it really just moisture and I have to live with this sound?