The best advice I can give when working with lines,,, is to be sure , when putting them back together , to thread it with your fingers... hold the line with one hand,, maybe jiggle it to get any sideforce off the nut.. then put the nut on with your fingers.. as far as you can ,,, then use your wrench just to tighten the correct amount... nothing worse than cross threading a metal line flare nut...