Good advice as above, but also check the sole clearance with the pedal. A lot of these type of shoes have the cleats mounted too deep from being inset into the sole, especially as you are running a low profile platform SPD pedal; the rubber outsole may act as an unwanted gasket preventing easy release rotation. Think of it as closing a door with too thick weatherstripping; you can close the door, but it takes extra effort to turn the doorknob and open it. You can try the shoes on a friend's non-platform SPDs and see if the problem persists. Worth a look and may possibly be solved with a sharp blade and a keen eye.