ST's FOC for BLDC start up errors
I guess, your motor has rotor of uniform shape and have glued permanent magnets. There is a certain problem detecting the rotor position for the sensorless method, as it is takes the advantage of the reluctance paths of the internal PMSM (I-PMSM) which has a "buried" permanent magnet in the stack laminations.



Your motor is probably SM-SMPM which has surface mounted (glued) magnets (blue) with very little gap. 

You would need to ad an encoder feedback, or change the motor with I-PMSM, as the new sensorless method uses the reluctance path of iron core to detect the position/speed.