Possible causes:
• Sensor positioned too far from the origin magnet
• Sensor and origin manget positioned at different heights
• Incorrect orientation of magnet inside enclosure
• More than one magnet on gate
• Incorrect orientation of origin magnet
• Magnetised item on rack
• Incorrect orientation of the electric motor is causing induction
• Missing pins on origin enclosure
• Faulty harness
• Faulty origin sensor