In my opinion, if the mounting system was at fault and caused the warping of the casting which led to failure, the cracks would have extended to the mounting lug(s). This type of failure is just surrounding the cylinder attachment. I can not see how the mounting system would cause this type of failure. I agree with the comments that a flaw in the castings allowed for a weak area which extended to cause this failure.

Just my 2 cents

Elson