Jim, Sorry your having troubles. I have had a few lines sent to me recently from the parts store that were copper/nickel and I have to say that they seem light weight to me and I thought that over tightening them may make them leak. I haven't had this happen, but I had the thought that it could....
I haven't re-flaired any of the copper flare lines so I can't say that I have any real world info on this subject. Just a hunch!
Good luck and I can appreciate how frustrating this is.
