Hi Mate heres the fix . Or one of them
Disassemble to caliper & measure the pistons , side to side.
I bet there oval, slightly.
This is a known problem & they stick when ever they want
Go to Pax racing or Powerband in the UK , not US, & order his stainless pistons
Also you might try putting a insulator material between the pad & piston .
That will help with pad heat transfer between the 2.
I use a ally coke can cut to the shape of the pad.
