Thanks. I used the methodology stated in the linked thread and found the problem. Long story short, I had created an Associative Intersection curve on a Face and constructed the cut plane on the fly. This was the culprit. Fixed it by creating a Datum Plane and using that for the Intersection. Boom!!
I should note that these three parts are cylindrical. There are planar face datums and cylindrical face datums and hole datums for clocking the hole pattern.
