I have a Mark 4 complete kit with standard brakes. My RR caliper sometimes will not fully release after I let off the brakes. I’ve taken the caliper off and looked at it and can not see anything odd. All the brake lines going to it are good with no pinches. I am wanting to replace the caliper but am not for sure what to buy. Can someone give me the year and make of what I should ask for at the parts store?