I got a bad "new" line once but it was probably very old. The plasticizers just leaked out and the line went from being very greasy to so dry that it wouldn't go through guides.
The Northern Sport Line Company of Ontario makes primarily private label, custom fly lines. I don't know if that would be the source of any e-bay lines but I wouldn't doubt it.
The first one that I remember buying was back around 1980. Still have it.
I have 7-8 others too.