It looks like you’re using the long 3M screw (about 25mm / 1 inch). Try using the shorter 3M screws (about 12mm / 0.5 inch).
Those long screws are used to attach the motors to the motor brackets. They are too long to use for the standoffs, as they will bottom out in the standoff (threaded about 11mm).
If it’s stuck, try using pliers on the head of the screw and on the standoff to get the screw out.