Grove Motor Driver (TB6612FNG) control stepper motor

Hi all,

I tried to control my stepper motor to rotate at a small angle ( ex: 45 degrees) and using the Grove Motor Driver (TB6612FNG). And it did not rotate correctly ( 2-3 degree difference). But when I make it rotate 1-2 round it will be exactly correct. I’m not putting any load on the motor. What would be the problems?

Thanks for the support.