[Sirrotica]

It''s not real common, but I have seen the flares crack. The crack is so fine you had to remove the lines and inspect them very carefully to see the crack.

I'm not saying this is it, but if all else fails you could have a cracked flare.

The more common problem is as has already been said. You need to tighten and loosen the fittings to seat them, especially new lines.

Stainless lines, it's almost a given that you're going to have to repeat the ritual. The harder the material of course the less malleable it is and getting the seats to mate takes more time and effort.