I'll post parts I changed on the Ant PCB mill here
-the head, The holes for the bearing are really to small and in addition it is better to have them clamp than really force them into the hole which will deform the bearing

• in general holes with support are printed better with the holes filled ith 1 layer. this can easily be removed
  yo ucan also use only 3 bearing instead of 4 which constrains it enough with less change of binding