Milling problem

Hi all,

I am new on this forum. I am using a D600 with a performance kit for 1 year.
For a few week, I have a problem with the milling. If I want a simple oval for example, the result is different.
Indeed, the milling is not homogeneous, sometimes 1,2 mm wide and sometimes 1,8 mm (see picture attached) like an axis doesn’t work correctly. But after controling everything today, the result is still the same.

Did you have a similar problem ?

Many thanks