I had the exact same issue with my rear brakes. Rust had formed on the caliper bracket underneath the clips. This caused the clips to press too tightly on the brake pads causing them to not release completely. The solution was to grind away the rust on the bracket, underneath the clips, and remove an additional 5 MM of material from the bracket Liberally coat the bracket underneath the clip with anti-seize to stop future rust. This allows the pads to move more freely and not drag. I also cleaned and greased, with synthetic brake grease, the caliper slide pins and thoroughly cleaned the holes or apertures that the pins slide into.
Fixed my brake issue.