1. Have you noticed e stop switch on the track or in the motor. Switches usually tell the chain or screw when to stop. If you d/n see it on the track, pull the cover and you might see contact points as your stop switch.
2. There are usually Up and Down Tension Screws marked on the unit to adjust the up and down force of Up/Down.
3. Open your Unit to see if your gears are in good condition that lift and lower the door.
4. Post a pic of the inside gears as attached and shows the travel contacts and force.