If the rings and base are within reason, the scope has to be bent or defective inside. Like I said before, 4 feet high at 20 yds would put the rear almost 1/4" higher than the front.
Never trust an arbor type boresighter, as the spuds can bend very easily. It is just as easy to bore sight looking through the bore and centering on a target at 50 feet and seeing where the scope is pointing.