Or perhaps a humidity test would help. Bake a screen to fix it, then put it next to a humidifier and see if it comes back. That would be additional observational data. Then if it comes back you can simply re-bake it to get rid of it. For those that think it's humidity, it should be an easy and safe test.
The reason I'm skeptical of moisture is that if there are gaps in the screen that cause moisture to enter, then why would baking it keep it away for over 6 months, especially when part of those 6 months are July, August, and September; very humid months. Wouldn't it just enter again when the pressure changes during some minute expansion of the panels, while sucking in air? Also, having seen the way vapor behaves between window panes, it doesn't disappear as orderly and timely as the LCD panel has done for me when shutting down and having it completely go away in a somewhat set period of time. I would think it might persist for much longer (days) around the edges depending on humidity conditions outside...i.e. during really humid times, wouldn't the tunneling just stay as is?
I'm not discounting it as a theory completely, but I feel like that's been the main fallback and thrown out there as fact. Heating and cooling between two close surfaces and their potential movement away from each other when not fastened together due to lack of sealant seems just as plausible and potentially could be more constant. As the screen warms up due to electricity flowing through it, the panels start minutely separating and that could be causing the constancy of the tunneling pattern. Just as heating could be vaporizing moisture between panels, so could it be re-flowing sealant, causing less movement between those panels. The latter would not be impacted by by outside condition. Why does vacuum sealing also work? Again, could be sucking out the moisture, or it could be pushing the panels together, thus creating a tighter bond (note, I've only heard anecdotal stories about someone trying that technique). Why does storing it in rice (or some other dehydration method) for 10 years work (that's one that I heard)? Well, again, that's a hard one, to say something worked because it was stored for 10 years. I mean, how was it stored? How bad was it before hand? Was it completely cured?