Garage door won't open or close when the opener light is on

Garage Door Opener Model: Lift-master 1245R (by Chamberlain)

Ok, so this has been quite the puzzle. Roughly a couple of months ago, one of my parents’ garage door openers started having problems. The problem was that the garage door seemed to open, but not close when using the remote(it worked fine with the wall button). I decided to do some testing to try to narrow down what the problem was. Rather than describe in too much detail the testing I did, I think I’ll just list some of the things I found that led me to my conclusion.

• The garage door remote is a two-button remote. The button for the other door works just fine.

• The other garage door opener(that is the exact same model) works just fine.

• I tried resetting the remote and reprogramming the buttons so that each button now worked for the other garage door(i.e. B1:GD1, B2:GD2 >>> B1:GD2, B2:GD1). No change.

• I tried reprogramming a different single-button remote to work with the door opener, that I know worked with the other door opener. Still no change.

• I thought that it might be some kind of signal interference, and did some research online. Considering that the other door opener doesn’t have any problems(and is closer to the rest of the house), I narrowed my search to nearby sources of interference. I checked to see if the florescent lights interfered by disconnecting them. No change.

• Finally, I noticed that strangely the remote would work to both open and close the garage door as long as the garage door openers light was off. I tried removing the light bulb(an incandescent) just to see if it itself was interfering. No change.

So the problem seems to have something to do with the electronics within the door opener and how they may or may not relate to the opener’s light being on. My current thinking is that it might have something to do with the control board, but I don’t know for sure. Before trying to open it up and completely replace the control board(which would likely be expensive to order), I thought I would see if anybody here has any ideas about what exactly is wrong and what could be done to fix it.

BTW before it gets suggested, after opening or closing the door the light stays on for around 4.5 minutes, which is a bit too long to just wait around for it to go back off every time you need to go somewhere.