[pastaman]

I'm thinking bent ball screw or the end work is not centered.

I know it sounds strange but loosen the bolts on the bearing support side of a screw and see if it gets better.

It could be either end.

I had a problem like that a few years ago. The end work was off center and the hole table would rock around and make waves in the cut. It got worse as you moved to the area with the bad end work.

I did a video of it.

https://www.youtube.com/watch?v=d3Gg7qDeFCY

I ran my DTI through the full table travel. I do have some droop (~.0015") at each end of the table but that doesn't surprise me. However, the needle does oscillate at each end of table travel. Not much just a few tenths. I'm thinking this is OK.