Verify that the safety sensor lights are both solidly lit (typically green and/ or amber when they are aligned correctly.)
The problem with the door closing and reopening itself can be a sign that the door is either binding on the track or hitting something, so the safety feature kicks in and reverses the door. Perform the following tests:First, I would close the door and then disconnect the door from the trolley and operate the door manually. The door NEEDS to roll smoothly and not bind on anything and it NEEDS to be balanced and stay at any point you stop it. If the door wants to go down by itself the springs are weak and at fault; have a qualified service technician fix/ adjust them...they can be very dangerous to work with since they are under extreme tension.Second, operate the motor unit without the door attached and see if it operates correctly. The trolley will fully go up and down if working properly.Performing these tests will help narrow down whether the door/ tracks are the problem or the motor unit is giving you the problem.Please let me know what you find from these tests and we can proceed from there.If you have any further questions, please feel free to let me know...Please rate my answer if I have completely helped you today, so that I am credited for my time assisting you. Rating my answer does not cost you any more, and only by your rating am I compensated.