How tight was the SF on the rack? If it rattled around, that could have put stress on the clip. It seems like the best mountings are totally compliant (like on the loop of a bag) or totally rigid (using the bracket that comes with the light), and not just for SF, but for all lights.
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I stop for people / whose right of way I honor / but not for no one.
Originally Posted by
bragi 
"However, it's never a good idea to overgeneralize."