motor cogging

[zeed]

Well,I have some strange problem with my diy desktop cnc.
Had some problems with calibrating Y axis,just could not get it right.On X and z axis did not had any problems,just my Y axis...
After a lot of work on mechanical parts discovered this strange problem.

When moving it manual (joging) it works flawless,but when comanding it from g-code(for example:G0Y150) motor after 3-4 seconds makes some strange noise,glitches for a moment and then continues rotating.
Sometimes it stalls but very rarely.
This tests are made with motor separated from the machine(leadscrew).

Tried switchin the drivers,same thing happens,also switching the motors makes no diference.
Even changed parallel port pins for that axis but no difference.
HELP please,because this cnc hoby is slowly becoming nightmare...

[ger21]

If the motor is mounted to the machine, it could be resonance. Resonance can be worse with the motor not connected to the screw. Try attaching the screw and see is it's better.