Should be nothing that will make a brim not round unless the model isnt – meaning almost certainly slop somewhere.
With this sort of issue, you may find a test cube more beneficial to test with that your current model. As its much easier to use to reference issues in either the X or Y axis. Also printing a hollow test cylinder will confirm if you your X isn’t perpendicular to Y.
Print still looks very sloppy by the way. Im sure we can do much much better.
Agin feel free to send your model stl file and gcode for me to test.