Please follow below steps to troubleshoot the problem:
1）Please confirm if the current of pulse signal by the controller is enough. Normally, the current should be over 10mA in order to make the optocoupler work steadily and signal transfer normally.
2）Please check if the frequency generated from the controller is too high to make the driver receive the signal.
3）Please confirm whether the starting frequency is too high or it has been set the acceleration process even though the acceleration time is very short; Otherwise, it may cause the motor operating unsteadily.
4）Please check if the motor is fix well. If not, it will result in the motor resonance heavily and then the motor loosing steps.
5）Please confirm if the connection of motor A、B wires is correct. Don’t forget the phase and ensure the connection to driver in good status.
6）Please confirm if the driving voltage is normal. It had better choose the typical, not over voltage or low voltage, which can avoid the shake when unloading.
7）Each motor has an resonance region at low speed, please ensure the motor doesn’t work at the resonance zone.