The "problem" it had early on was one wing or large section of it departing the rest of the sructure in flight resulting in 3 or more fatal crashes which is a pretty significant problem. I believe it was the last US airliner built without being put through a static fatigue test which should have shown up the flaws in the wing and nacelle design. Given the relatively low number built and the cost of the fix for the "problem" Lockheed probably lost money on the program as they did with the L1011.