The motor knows where to stop through stored limit positions. If the shutter stops early, the limits may have been lost after a power fault, or the curtain may be catching in the guides, which makes the motor sense resistance and stop. Check for debris in the tracks first. If the track is clear, the limits can usually be reset by a technician. Please avoid forcing the shutter by hand, since a bent slat or damaged guide will cause the same fault again and can harm the motor.
