I want to know as follow question:
1 If the machine frame is welded by yourself in your shop?
2 Do you cut these part are very perfectly?
3 I think impropriety setting cause this result.for example your x/y Ramping Rate and Continous Contouring Feedrate.becase rotate the part change the machine's move contrail,please see picture A.
I hope that can help you solve problem.