Thanks for all the suggestions. To answer a couple queries: I've probably installed/removed this FW a total of three times. Mostly I changed it out when I had an epic hilly day planned. Never a problem with removal; in fact, I put in the tool, placed my huge crescent wrench on it and voila! Done. No fuss. I didn't even have a problem removing the broken unit from the hub after the event, even though there was barely any spline left at the break.

Bob, you make some interesting points. And no, this was never serviced by you (just that alloy Zeus). I have to think in the end it was a metallurgy issue - and yeah, the break is clean. No dark spot in one place indicating a metal flaw. Pawls were in good shape and not stuck. Overall a very clean unit.

I am sure of one thing: it was not my leg power. My legs don't have much power these days

I will keep a close eye on my other CX; most of my remaining close-ratio FWs are Reginas, and they are Oros for the most part.

DD