I built my Lowrider about 18 months ago, got it working but didn’t have a chance to use it properly until recently. I was dismayed to find it not tracking properly, even after building a squaring jig. It would track about -ve X 5mm after going about 300mm +ve Y. But would track back to zero (home) OK. And issue was repeatable.
Logged on to forum to seek help and found this thread. So grateful - immediately diagnosed my issue. I verified it was a wheel (roller) alignment issue. I looked at the solution - they seemed a bit involved.
For what it is worth, I simply mounted aluminum angle section (25 x 20mm x 1.6mm thick) parallel to Y. Rollers track to the inside of the vertical portion of angle. Cheap and easy. Works perfectly - have perfect tracking in Y now. No evidence of rollers binding . See in photos.
Thank you to forum contributors!!