I bought new PVC back door that opens outward and fitted it myself. the frame is plumed all round. The door closes with no issues. however, the sash is not sitting squarely inside the frame. I had hoped to get good 8mm all round the sash but it is not. The worse, corner is the left bottom corner (hinge side) the sash barely touching the frame (1mm), see attached pic. there are three alan keys in the hinge one on the side which move the sash side ways and tow on the top, the outer one is the pin that hold the door and it moves the door in and out but the third one done nothing. I had hope it moves the frame up and down. how can I lower the right bottom corner (hinge side)