Prop Problem?

I've got a problem which has stumped a lot of very talented, experienced, bright folks, and was wondering if anyone has run into a similar problem over the years.

Background: Two unknown quantities: Different rear engine (low time), overhauled rear prop and governor. Everything worked fine on old engine, prop, and governor.

Now: I'll fly for 1 hour, get it hot, land, let it sit for half hour . . . start it up, and after about 10 minutes on the ground, the rear prop goes, and stays in feather position.

It originally happened to me a few of weeks ago on a LA mission, and I was stranded. Let it cool long enough (overnight), and I can start the engine, take out of feather, and fly away. But . . . after I fly for an hour and let it sit for a half hour or so on ground, it repeats itself. No problem at all when I land and taxi, no feather or loss of RPM issues. But, let it sit for half hour, and it feathers after about 10 minutes.

It's never feathered on me in flight . . . yet.

No, I'm not still flying it . . . I've just tried the following.

Had governor checked by prop shop, and returned to service and yellow tagged -- I tried to fly it and the same thing happened.
They swear it ain't the governor!

Called Continental because the prop shop swore it was a defective area around the main bearing transfer area.
Continental sent me a Technical Brief to check for oil pressure. IA performed test per Technical Brief. Minimum pressure differential was supposed to be 12/80. Test resulted in 27/80. Passed with flying colors. (Continental thinks its a prop problem).

Prop shop took propellor back, changed out more parts, and sent it back returned to service, yellow tagged and re-sealed.

Flew today, and same thing happened.

So . . . what say all of you experienced Skymaster folks? I'm stumped, IA is stumped (still thinks it's a prop problem), and clearly, the prop shop is stumped.

I'm checking with other prop shops, but am wondering if the same scenario has happened to anyone else in the history of Skymaster kind.

Thanks,

Keven
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