Braided Loop
For me; the braided loop is generally not the problem. It's usually the fly line right above the connection. The fly line starts to crack and that lets the line hinge. This usually ends up cracking around the whole line exposing the core.
I just cut it back and add another braided loop. It usually lasts about a season or so.
Touche, the exact same thing has happened to most of my braided loops over time, using a nail knot or shrink tube. I think the line tends to hinge more at the end of the nail knot, shrink tube area and thus eventually cracking over time. The nail knot or shrink tube also cinches down on the line coating, helping the line to crack in this area also.
I have had the base area of welded loops do the same thing, because that is the hinge area again, I think.
One of the reasons I prefer a core spliced loop if the line has a braided core. The core spliced loop tends to hinge at the core line loop base, not on the line coating. Also, the core spliced loop pulls from the line core, not the line coating. So the line coating is a lot less prone to crack using a core spliced loop.
A core spliced loop also slides through the rod guides easier, no catching, than any fly line loop I have tried.