I have the garage sensor installed and it worked perfectly for about a month until the weather turned cold. Now the status flaps between open and closed about once per minute or more. The only thing that has changed is the weather. With the car in the garage and the door closed I should read about 125cm. I can watch it jump between about 55 and 125 back and forth with nothing changing below it.
Not sure what’s causing it, but I suspect it may be due to multiple reflections of the ultrasonic wave in the room which resulted in the error in distance sensing. It could be affected by temperature. You can submit a support ticket and arrange for a replacement, to see if it makes any difference.