Star PD .45 ACP defect

I recently was given a Star PD .45 ACP. I did some reading up about it and most of the reviews were great. It was a good 1911 made from 1975 to 1990. Unfortunately mine has not lived up to that expectation. It seems to shoot incredibly low and then about once every 4 or 5 shots it shoots right on target. At first I thought it had to be the ammo, but I've since tried 3 or 4 different brands and each one has given me the same result. A buddy of mine heard about the recoil buffers being bad on this gun. I couldn't find much information about this though. If anybody knows what the problem is or how to fix it that would be much appreciated.