Originally Posted by WhyFi

Stuff happens fast and not all sticks are nicely uniform, so I wouldn't expect damage to be neat and symmetrical, either. Maybe it was thicker and stronger on one end. Maybe it was branched and the force more diffused on the other side. Maybe it was a long branch, only the tip got caught up, and the leverage from the rest of the branch was enough to crack the stay before it got flung behind. Maybe it went in cock-eyed, etc, etc. Any of that is more plausible than it just buckling in that manner while riding around.