Pete i don't think the issue is with heat and CAS. i say that because the engine today and a couple of other times has only been running for less than 10mins.
I am suspecting the CAS still, even though it is only 2 years old and Delphi.
I did have a belt shred a fair while back and some of the steel strings wrapped inside the balancer. I had some running rough issues but that stopped once i fished out the strings.
I am wondering if one might still be caught up inside. I also suspect i have a weeping crank seal although without pulling the balancer i can't confirm that. I read that
@immortality described an issue with oil around the sensor doing a similar thing.
FX i doubt the balancer rubber is the problem as you tend to know on the V6 if the balancer is buggard.