stepper motor stalling after 56 clockwise rotation

[guangwei xing]

Dear all,

May I ask if someone met the stalling situation before?

I tested the stepper motor with a python code via serial communication. Rotate the stepper motor 90 degrees with a move command every 5 seconds. However, every time after 56 circles, the stepper motor stalled.  There is no load, and the micro-stepping is set at 128. 

Thanks in advance for your help.

Regards

Guangwei