Stainless braided trans lines

I got a new of stainless steel braided transmission lines with 6an fitting on the transmission side and 6 SAE fittings (5/16 inverted flare) on the radiator. I got them on ebay and one was about 12" too long, I had asked if I could send it back and simply get a new one 12" shorter with the same fittings, instead he suggested that I cut the line and he would send me an aeroquip 6an reusable fitting. So I followed the instructions put it in and no problems for about a week, then it started leaking. I pulled it off cut it again and put the fitting back according to the instructions, it worked again for about a week, now it is leaking again. The guy is no longer on ebay and won't answer my e-mails. So I need to find somewhere that will make a custom line with appropriate the fittings on each end. or some suggestions on how to make the fittings I have work, or new leak proof fittings. Thanks

Greg