All of the above! But while you have the neck off, turn the screws back into the body holes. If they "tighten" just keep turning a little harder and the screws will actually act as a drill to remove the slight interference from the body holes. Just turn them until they turn freely in the body. THEN, place the neck back on and start threading the screws back into the neck itself, but rotate the tightening so each screw pulls the neck down a small amount each time. Once the neck touches the body, check to make sure it is flat and in full contact and then torque the screws to their final tightness. If that doesn't work, there would have to be warpage of the neck heel, which certainly would warrant return of the guitar!