Interesting to see that it's a Suntour RDO. I guess it's true that Suntour DOs have a tendency to crack. I've seen many other cases of cracking with Suntour's RDO in the net already in the past few years. At least it's the only real dud product to have come out from the company. Maybe their design just had too big a cutout and does not have enough material around it to stand up to normal stresses, or could it be bad steel? Simplex RDOs look so much more robust in comparison.

Chombi