Hi Leo and
to the forum.
If the motor only begins to turn at over 1/2 to 3/4 throttle movement, I suspect there may be a problem with a low +5V supply to the throttle unit coming from the controller.
If you unplug the Pedelec sensor
(which also draws its current from the same +5V supply), you may find that the rpm will increase.
If this is the case, I suspect that the controller or the Pedelec unit may be at fault.
The programming lead also draws power from this +5V supply, but if it is too low, it may not be sufficient to operate the correct programming function of the controller's chip correctly.
You can hopefully measure the voltage of the +5V supply between the Black and Red wires on the Pedelec connector, which should be at least 3.5~4.0V.
A minimum of 3.25V is required on the throttle signal wire to achieve the maximum motor rpm.
Alan