the last pic with the pad in hand you can see the tab / ear hs been in tight and i would bet the o.p. had to pry it out of the bracket . most of the time this is the case but not always .
also its NOT just gm with the problem .
the bracket the pads sit in gets rusted up and binds up the pads in the bracket so they cant float and move the way they need to . also lots of brake pads these days need the extra flashing filed / ground / removed to make sure the pads float .
i clean the bracket down to bare metal in a blast cabinet or small grinder wheel or bit . then new shim unit installed . next test fit the new pads and make them fit with a little slop in the bracket so they float good and ave room before the rust builds up and locks them in again .
once this is done i remove the pads / shim unit and coat the surfaces in copper anti-seize . then shim back on and a little copper anti-seize and pads .
once the rotors are rusted this way there junk / wont clean up with new pads or even on a rotor resurface machine . i ran one for almost 15 years i tried a few times and by the time you get a good surface your so far under min spec the rotor is junk . so just get new .
before the rotor goes on the wheel hub or axle flange make sure the surface is clean and not rusted bad . then a coat of anti-seize to let the rotor float and not rust up on to the hub center . the rotor needs to float or it will warp .
all this work is NOT covered under you std auto shop brake job . they just hang them and bang them out .
people wounder why i take over 1 hr to do a set of pads / rotors on 1 axle . but i dont have come back jobs and my jobs last longer before they need redone again .
hope this info helps and good luck . 41 years of living and working in the rust belt of the north east here .
