The second part of your question, doesn't have an answer.
Nor does it deserve one. How could it.
Michael - you are an expert and maybe you have inside info on who made it as being another pro who would only do a faultless install. But as a general comment, that was a little brusque.
Is the tenon centered? (as opposed to ferule being thin on one side fat on the other)
Was the fit a "good" fit - thin glueline and no voids?
How thin are the ferule walls? IOW, what is the tenon dia vs the OD of the ferule?
As another possibility even if the ferule was centered as built, it might have been user induced if you ever had the shaft reduced. Only one of mine that cracked was due to that. I drill most shafts. When a customer later requested an additional pro-taper shaft with slightly reduced dia, i told him i would make one but it might take a while. He went to a tournament and had one of the set-up mechanics there reduce the existing shaft. Actually, even then the thin-wall capped ferule survived, but a couple months later the hollow shaft cracked - it was turned slightly off center, and of course thinner than my design accounted for.
smt