2 mm makes a fatal

Y axis that has already finished forced to be dismantled because of trifles. It’s cause by 2mm problem. So, how the 2mm can make the big trouble so that i’m must dismantle and redesign the Y Axis?

At above picture we can see that at left and right of screw rod haven’t same distance. Left side 17 cm, right 17,2 cm. The difference only 2mm but…..that is a problem. This 2mm will make the Y axis moving with not stable and doing zig zag.
