@wummelfrosch
Thanks for the idea.
I have tried measuring with Digital calipers the distance between bottom of X rod and top of Y and ended up with L=66.68, R=66.8 and also top of X rod and bottom of Y rod L82.7 R82.77 which is off but not considerably and I don't really trust I can measure very accurately.
What I have noticed though is that the distance between the two X rods is 36.88 on the far left and right but nearer to the X carriage it goes to up to as high as 37.3 so I think the X carriage bearings are not spaced correctly and stretching the rods apart. So that could be it. though if this was affecting the levelling I would have thought it would be a curve along X rather than a slant consistent the whole way.