Rotor starts in wrong direction sometimes.

[BlachaL]

I'm using an STM32G431 and MCSDK 6.4.1. It's a 340 VDC BLDC motor with two pairs of magnets, running in FOC mode with HAL sensors. The motor works well most of the time, but it often starts in the wrong direction and then returns to the correct direction after a few revolutions. This happens when trying to move forward or backward. Sometimes the motor goes into "hard commutation"—the current is higher at about half the normal current, and a sound indicates that the rotation isn't as smooth as usual. I tried adjusting the HALL_PHASE_SHIFT setting in 15-degree increments and settled on the smoothest rotation in both directions. Debugging the HAL sensors showed stable sector readings in both directions and no interference in these signals.

What else can I try to make rotations reliable? Would an oscilloscope help?

[GMA]

Hello @BlachaL,

ST Motor profiler provides a HALL Sensor profiler. 
For more information, see the wiki page.

[BlachaL]

By adjusting the PID parameters, I was able to achieve more controlled RPM. However, I still have trouble starting the motor after the previous action was to stop it at high torque (tightening the screw). Loosening it sometimes causes it to start in the wrong direction and then reverse in the right direction.

[GMA]

Hello ​@BlachaL,

Are you still using the MCSDK6.4.1 version?
Could you try with the MCSDK6.4.2? As mentioned in the Specific changes introduced in the ST Motor Control Workbench chapter of the MCSDK release note: 
Improved Open to Closed loop transition overshoot behavior thanks to current and speed PIDs anti-windup feature.