It is uncommon for a copper patina to rub/get occasionally polished off.
It is possible, don't get me wrong, I have heard of this happening to others before, people unable
to get a copper light to patina for them. The discoloration/patina near the QR might be a mix of copper,
stainless steel, and Brass that can build up over time. Jason sells a product called Sunshine cloth.
It will bring Brass and Copper back to a bright shine easily.
Be sure the socket where the QR engages is free of foreign materials. Excess water/oils can attract
debris that can get pressed into and adhered to the end of the socket and flat edge of the Male QR.
A picture of yours would help others to better reply