Hi, I have a Chamberlain door opener, and recently the openers would not open the door, I thought the batteries were gone so I replaced them, that still did not work, I called Chamberlain for support, he told me to check the sensors, and I did and noticed that my son had accidently knocked one out of of whack, so I adjusted it and the door started opening again with the remotes, but only lasted for about 2 hours and then they would not open it again, I have tried several times to adjust them and they work for about 30 min or so and they will not open the door again, what else should I try?