Air Conditioner Jeep Cherokee

I have a problem with my 2001 Jeep Cherokee Air Conditioner?
It works very well when I go over 30 mph, but if I slow down or stuck in traffic after a few minutes it will stop blowing cold and you get a musky smell with a significant increase in moisture. Once you return to the speed it will start to blow mound after a few miles. Any ideas on what is wrong? Thank you.
A / C accumulator can be blocked or evaporator isn't working properly
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