The worst kites that I have owned/seen were the 2002 Gaastra GXS and GSpot. They had a flat section in the center of the leading edge which had a spar fitted to it, and when under load, at either end of the spar the LE would bend and crease and after a certain amount of use cause a massive blow out at the crease, usually while being launched or relaunching[}:)]
Even without the spar fitted the LE would still bend/crease/BLOW
I had 3 GXS kites, and know of 3 GSpots, all blew out in the exact same place on the LE.
This obvious design fault was not considered warranty issue either, so it was just BAD all round.

PS. the early Sonics weren't much better either