If your garage door is closing fully and then reversing to open again then it may be due to a problem with the close limit switch.
How to fix a belt drive garage door opener.
Replace the main gear drive if the garage door opener makes a grinding noise but the door doesn t move your main drive gear is probably toast.
You may have to fully remove the traveler slider from the unit to get the belt free depending on your model of garage door opener.
Garage door opener won t open all the way fix.
Step 7 check for repair.
Once you have the belt fully disassembled you can inspect the belt for repair.
Check the owner s manual for those details.
The main drive gear is the plastic gear that comes in direct contact with the worm drive gear on the motor.
In order to fix this you ll want to make small changes to the close limit setting until the door opener knows to stop once the door has reached the floor.