front caliper issues.

[thegeensnot]

Had a few past issues with my front brakes. finally thought i had solved my problems. but the top piston of the 2 isnt coming out when pressures applied. ive already drained system, removes pistons, cleaned calipers and piston chambers, replaced piston seals and rebled system and the problem is still occuring. any1 got any ideas why this is happening.

[mozer]

Im not too familiar with brakes but is there a passage that links the chambers that may be blocked??
Or does the piston move in and out manually? The reason i ask this is because i has a piston that was out-of-round that caused it to stick. I think a previous owner had used mole grips to remove it at some point and squashed it a little,just enough for it not to work properly