Damn....the problem came back!
there must be something wrong here....

Today I strated again the CNC and the problem I was facing yesterday came back...at which ever speed I drive the machine , there is every second a brief noize which is like if the stepper was loosing the stepp or giving shock to the ballscew. this results is poor speed and even machine blocking ( I mean stepper lock).
any idea of what can be wrong here?
the pulse is set to 35000hz and it is running at 35250hz so that should not be the issue.
the min step up time was set to 5uS, I tried 1uS, 2uS, and even 25uS...nothing to do...same issue.