Z Axis Movement Issues

Hey all, I’m having trouble with the x carve not cutting as clean as I believe that it should. One problem I’m having is the router shifts left and right as the z axis is moving up and down. It’s causing lines not to be straight and it’s causing issues with some of the corners. I also attached a picture of a sign I’m trying to carve and the name does not have clean lines. Any help would be greatly appreciated.

Your threaded rod may be bent