No, you didn't fail because of a manufacturing defect on the tie bar.
Your flight characteristics merely exceeded the tensile/shear strength of the tie bar.
Congrats on L1. Part of the adventure is learning what works and what doesn't. You learned what everyone else has learned (or read about), that these are poorly designed and usually just cut off and replaced with eye bolts (with fender washers) or just a shock cord simply passed through.
It often helps to watch what others are doing and learn from their success, but more importantly, their mistakes, so you do not make your own. I made a lot of rocketry mistakes growing up, but now I think twice about what I am doing before I do it.. Usually works out well.
Have fun!
