Recently the door would occasionally reverse when closing. Yesterday I couldn't make it close by pulling on it (figured the tension might be wrong). Disconnect and it would almost fall shut so no friction problem. Been awhile so I cleaned the IR sender/sensor. Closed. Aha! fixed it...nope. Did the same this morning. Tested the indicator light - yep, it is seeing the sendor. Cleaned again, door still won't close. Was just heading for the house when I noticed this little bitty sprig of cheatgrass with a flimsy head on it leaning in the door. Picked it and door fixed! That explained why it was intermittent - depended on how the breeze was blowing. It may have degraded the signal by about 50% which was apparently enough.
Harry K