your caliper is getting hung up , it can happen , you free it , hit the breaks and it doesnt return , you can get a rebuild kit from most auto shops but it isnt a sure fix, but they are alot cheaper. A semi loaded caliper is one that comes with all necc hardware but no pads, a fully loaded caliper comes with all hardware and pads.
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I work as a partsman in the BC Area if you need help finding something you cant find pm me here and i will see what i can do.
www.lordco.com
Better to sit in silence and be thought stupid , then to open your mouth and remove all doubt.