Without pushing your luck, try reducing PD011 to 100 from 120 to see if this has some effect.
I think this is the minimum speed (frequency) 2 poles @ 100 = 6000RPM, if my mental arithmetic is still working.
If the minimum speed is set too low, it is possible to cook some motors, as the frequency is too low, for the inductance of the motor, causing too much heating.
If you keep increasing the speed, once above this speed the down button should reduce speed back to this minimum value.
For 2 pole, 120Hz is 7200RPM.