2lt cast pistons on std rods

[joe84]

a problem that seems to keep happening with my engines is the piston pin seems to wear a groove into the piston , so they become stiff , ie the piston won't roll side to side on it's own weight, usually it's just been 1 piston but this time it's 3 out of 4, is this a problem when it is pressed together ??? i've had them done at different places but still seems re-occur, i'm guessing it wears the bore into an oval pretty fast especially how stiff no.1 was, i don't really have anything to accurately measure the bores, is this just the downside to the press fit?

cheers