3d prints come up with ribbing on one side
Hmmmm In my experience when a printer has that bad of wobble it is still the Z axis. Your rods might be good, but are the two Z axis the exact correct distance and equal distance on the printer frame? Imagine that you had one a few millimeters too far out. How might the rods act? Mayhaps, over the course of several layers, they would slowly drift back and forth? Creating a period effect on your print? What do the top of the rods do over time? Do they move a lot if you go from height 0 to 100mm on z?
I have a few ideas. What happens if you loosen you Z motors so they can move around their mount? I had to do that on my Prusa back in the day. I think for that machine the Belt was actually too tight causing the issue. Current printers are usually better designed so its unlikely that is your issue. Also measure the distance between the top of the rods when the carriage is at 0, and at max. You should see very little variance.
If it was on both sides I would say it was bad PID calibration. IE this simplify 3d link
Though you can see on this forum the fellow had a bad coupler. So still mechanical.
Also could be back lash / belt lash.. but unlikely