Update:

Thanks for the suggestions everyone.

I kept playing around with the FD cable tension and limit screws settings. Nothing was helping.

Then on Sunday morning after another round of tweaks, I tightened the FD cable bolt, and the bolt hole at the top of the FD snapped right off. Doh!

Did I overtighten? Was the FD failing, and was that the cause of the shifting problem?

I bought a new Campy Centaur FD on ebay (old one was Chorus), currently being shipped.

Will the shifting issue disappear with a new FD? To be continued ...