Really, stainless steel is unsuitable for brake and fuel lines. Its tensile strength and hardness practically guarantee leaks at every joint. So, since it is so stubborn, you have to just back off the nut, tighten, back off, tighten until it gives in. It may look pretty and be touted as corrosion proof, but the newer nickel alloy stuff does the same thing, shines up really nice, and works much smoother.
