I have had a similar experience with my Vesper on my G1. After ~6 months of fiddling with the preload nut I was able to dial in an appropriate preload with the rotor removed and the bike in-stand while freewheeling. That nut position would last a few rides until self-loosening, but ultimately held position with some blue loctite. Those 6 months of hub faff likely contributed to early bearing failures.
Tangentially, I'm currently mid-warranty with Onyx about a similar chain suck/freewheel friction issue. I believe the elastomer cage of the sprag assembly failed and tiny pieces of elastomer became lodged between the sprags and the inner race. Have you pulled out the driver to check on the condition of the sprags?
Its pretty disappointing, particularly considering this hub was a new replacement after a spoke somehow managed to pull through the flange material this time last year. Ever seen a hub flange shear before a J bend?
It's been a hefty price to pay for the sound of silence.