have you tried being closer to the box when you use the remote? I would hope that the closer you get the more responsive ... which I presume should give a better indication that the problem is interference... Also moving the box if possible ...
I didn't go any further into reading the links (other than the basic problem, though one person tried putting incandescent bulbs into a light fixture near the problem, and they saw that was the cause) ... but thoughts would be to try to mitegate or prove the issue.. light (physical) may be blocked by a piece of cardboard creating a "visor" for the receiver ... either above or below it.. or a metal sheet if more than just the visual (infrared) ... just for testing.. have a cookie/baking sheet in the house? ... just thoughts.. no hard sciences thought to it..