It seems to be all breaking around that part of the tube. could it be a bad welding job that stressed that joint there?? I better check mine before I start riding in the beginning of my season in April just to make sure everything is tip top. If I ever see a crack i’ll call up ming and hopefully they can mail me a new bottom tube with that new BB that has a massive weld all around it. 
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We’ve had far less frame cracks than the other major folders it seems (dahon, brompton, bike friday(recall fix)) they where all on the seatpost which we don’t have such a design.