Had the exact same problem with a SA GPX with the welded loop. Sent it in and SA replaced it no questions asked. Sadly this was the second SA GPX line I have had the exact same thing happen to, though SA replaced both lines it was an inconvenience. It certainly seems to be an issue with the welded loop on these lines as like you the one I had to replace most recently it had been fished maybe 4 times.
Brian
"My father was very sure about certain matters pertaining to the universe. To him, all good things - trout as well as eternal salvation - come by grace and grace comes by art and art does not come easy." Norman Maclean, A River Runs Through It