problem with stepper motot driver (2 replies)

Hi,
I have a problem with my steppper motor driver ( see the picture of the driver in the attachement ) when increase the frequency of PUL signal up to 150 khz the motor did not rotate and make a noise but when i shake the PUL wire it works, when the frequency is 125 khz it works as usual , by the way the maximum frequency that the driver can support is 200 khz .