I Noticed i am not getting perfect circles though i am 1/4 off on the x or y axis.
Just a thought.
Cut a square larger the better and check it with a machinist or carpenters square. You may need to re align the gantry X to the Y axis on the table.
That looks really good- cool design. I don’t see any evidence of missed steps or backlash so out of square gantry is fhe likely culprit. We align these in our fixtures, but some of the alignment precision can be ‘lost’ during the gantry leveling step where the 8 bolts get broke loose. Easy to adjust though. Cutting a square and measuring diagonals is probably your best bet.
How is that fixed to the rim?