odd z wobble

I don't know if this should go in fix my printer or fix my print...I have an odd z-wobble issue, the z-wobble only happens at the extremes of the x axis and not in the y…sort of. The z axis is belt driven so there is no bent lead screw but there is unmistakeable banding at the same pitch pitch as the gt2 belts used for x,y,z axes. Any idea what might cause this? Hatchbox pla, 210c, .3 layer, dragon dual switching hotends, .6 Bondtech cht nozzle