Haha yeah, it would make sense for the X10 module to be installed in a reasonably accessible location. However, I looked everywhere (except that ceiling path) and could not find it. As such, I couldn't try rotating the house code on the module. I'm going to try crawling in there later, but as it is it doesn't look feasible.
We have two wall switches in the room, and after taking out both, I failed to find the X10 module behind either. I did make another discovery that confuses me even more though:
Over the course of 3 days, I tried troubleshooting the lights to see if I could get some consistent results, but unfortunately they have been anything but.
- On the first day, turning on one of the sets of lights with its wall switch would cause it not to turn off when pressing "All Off" on the IR543, but it would respond to "All On" after turning it off with the wall switch. This problem dissipated after a night's sleep.
- On the second day, I tried repeating the above, but the lights were properly responding to commands. The same happened with the third day.
It's difficult to find a problem's source when I can't even get consistent testing results. I might have to bring in a professional's help.