DRV8818EVM: Current waveforms overlap

Hi Team,

This is a board designed by the customer himself. DRV8818 sets 1/8 microstep, Vdecay=2.6V, Vcc=5V, Rx=27K, Cx=680pF, SRn=0, STEP=4KHz

But the motor vibrates and makes a lot of noise. The captured curve of the ISEN sampling resistor is as follows:

May I ask what is the reason for this?How to solve it?

Thanks,

Annie