this is unbelievable.
i took the spoiler apart, and found out that the extra wires going to the motor, are actually going to a switch, that seats on the rail.
there goes my "knock sensor" theory.
the switch basically detects the movement of the mechanistic, and send command to the clusters . very old school in my opinion.
could be the switch in my spoiler is defected, that's why it works only manually.
this is the switch (yellow arrow):
having a look at the way the mechanistic is build, i don't think there is a way to make it work faster. the motor spins a gear that spins a spiral cable, so you are loosing speed, but the motor gets the required torque to push and pull the spoiler.