You should always make sure the caliper retaining clip is clean..I mean super clean and free of any burrs, notches, rust, dirt etc. This is what gives your rear brakes thier smooth action and keeps them from hanging up.
It is critical to remove them everytime you change your pads and clean up the rust on the carrier as indicated in the pics. It would also be wise to apply either a thin layer of high temp grease or anti sieze below the anti rattle clip/ caliper retaining clip.
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