Sears garage door opener
My fairly new Sears garage door opener has recently started to "slip" down about four inches after it reaches the top of its travel path. The movement reactivates the motor and the door returns to its topmost position - sometimes this cycle happens only once or twice per opening but it has cycled like this repeatedly on several occasions. I tried increasing the upward force adjustment slightly but that didn't seem to help. Is this a spring issue ? They both look OK and are neither very old or broken.