At first, when I read your story, I thought ... "no way!" But then immediately remembered a couple months ago we were camped at a State Park in Indiana and every 20 minutes on the dot, the television would turn off. After several times of it turning off on its own, I timed it, and sure enough, exactly 20 minutes apart. Got home and never did it again.
So yea, it's possible something is emitting from your camper. As suggested above, unplug all power, see if the garage door opener works then. Then power up the trailer with everything turned off, and one by one see if you can isolate the root cause.
Either that or ... my second thought after the, "no way" moment .... Aliens --- the outer space kind!
