Since you've virtually eliminated installation as a factor (you use a connector which hasn't failed), you're left with few possibilities. Unless you bought all the chains together on within a narrow time interval, defective chains are likewise unlikely (what are the odds of buying 3 defective chains).
It's possible that you're cutting the chains too short (LT big/big+ 1"), but that's easy enough to rule in or out.
So, we're down to something about the sprockets, and you.
Question, this bike is Hyperglide, what were your prior bikes? If not Hyperglide, then I see that as the difference. Hyperglide makes overly aggressive possible, and can break chains in a way that non hyperglide bikes can't.
BTW- you never said whether the breaks were off the pin type or fractured plates.
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