The plane had a meter long piece of the wing clipped off several years ago in a ground collision. I’m no metallurgist, but I would think a jolt like that could leave a undetectable hairline crack near the fuselage.
NDT. Non destructive testing. Bore scope, X-Ray, Mag Particle, and Ultrasonic Thickness testing are just a few test applied in that very situation and any weakness or cracking would have been spotted. NDE/NDT is what I do for a living..