That makes sense. Thanks.
I must have been lucky with mine. I optically zeroed a Bushnell ultra HD 4.5-14 before mounting and only needed to adjust for elevation to the zero range.
It's my favourite pcp combo

I understand what you are saying Rog. Though, when the moderator is pushed onto the barrel and locates squarely into the shroud, the barrel should centralise in the shroud as a rigid assembly, hence my suggestion concerning the barrel band alignment and the link to video. Am I missing something? Chris

It is indeed.
The principle should apply equally to the s510 US barrel support, and certainly worth checking.

Have you checked the barrel clamp grub screws for tightness.?
Maybe the barrel has moved off centre.
https://www.youtube.com/watch?v=LNdYqVHiRBg