Interesting. The bend back in the wire is under quite a bit of tension and I wonder if it loosens the binding thread over time. I am very surprised that the double over wire would pull out even with a moderate amount of thread over top, especially with no junctions in the thread. I am going to dig out a few I've had sitting around for a while and see how they do in the slow pull test. Thanks again for the heads up.

I'll send you a few replacements.