I just hung a pre-hung fiberglass door with two side-lights. After
installing the door, it appears there is a 1/2" to 3/4" gap at the top
between the pre-hung header jam and the door slab. The sill and the bottom
of the door slab also rubs just slightly. The door handle side is perfectly
even with its opposing strike jamb. The hinge jamb is also even with it's
opposing left door slab. Doesn't make sense that this is an installation
issue, but the company that sold me the door swares it is, and will not
repair it.

The only thing I can figure is that the door was manufactured not square.
The header may have been manufactured slightly bowed or unleveled (higher at
one end). I can no longer move the prehung door unit as it is firmly in
place. Is there a way to fix this another way? The weatherstipping does not
cover the top to completely hide the outside and even after I apply the
molding, you can still see this space at the top even if the weatherstipping
did seal it. Besides the door does rub slightly at the sill causing a
functionality problem.

Thanks.