Looking at the cross section of the broken screws, they appear to have been over torqued to almost the point of failure... For some reason, Keystone ran these TEK screws up into the vertical flange of the frame, far exceeding the capabilities of TEKS...
By spec, TEKS are not to be used in material thicker than the length of the drill point section of the screw....(39 year career in the fastener industry)
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