Front right Z motor not working

Hello,

My front right Z motor of my VCORE 3 300 almost never works whenever i start my printer.
For example i start the homing / tilt procedure and the motor is not working (no torque, no enable signal?).
Altough once it starts working ... it works perfectly ... I have no idea how to start debugging this since ultimately it is able to work properly.
I always try the stepper buzzing command before printing to make sure the motor will be working.

Any ideas? suggestions? Thanks in advance.