The copper grease is located where the plate is behind the pads? Do you think it's enough to smooth the edges?Its not an uncommon thing. I'd take the pads out, inspect and lightly capmpher the edge of the material with a metal file. I use high temp copper grease on the retaining pin.
You could always just report it to the dealer If under warranty. I suspect that hard use of the brakes would eventually get rid of the noise.
