the wrist pin shouldn't be rotating in the piston at all. that galling looks like it came from too tight of a tolerance, you 'sanded the pin down'? they also usually have a precision ground finish from the factory.. when i have to re-size pins i put them in a lathe and use 400,600, then 1200 grit emory cloth to put a good finish back on them. i would guess the pin heated up and bound in the bearing.