RE: Skewed XY-Plane (Z Rods, Heatbed)
So over the weekend I built my Core One. [...]
It is a real bummer that there is such poor quality at the leadscrews. [...]
I take it that this was also a newly received Core One kit (i.e. you did not have it in storage for a few months)? If so, that would really be disappointing QC on Prusa's part, and apparently a total lack of feedback from their support team to production.
They should have learned from customer feedback in the meantime, and either have established dedicated checks that all three lead screws have the same pitch -- or at least stopped the practice of combining the pre-packaged MK4 motor kits with a separate motor, presumably from a different production lot.
RE: Skewed XY-Plane (Z Rods, Heatbed)
I ordered it Nov 20th during black Friday sale. When they announced the Plus version I hit the button. Received it last week. So brand new. Or maybe a kit which was in stock and they only added the Plus addon. I have to check the calibration sheet when everything was checked...