SOLVED LCD losing contrast over time

I've mostly been doing 5-6 hour prints tops, so haven't really noticed this until now, but...

The RRW graphic LCD included with the BigBox appears to have one big bug - the longer it's on, the lower its contrast gets. I've been running several 8 hour prints back-to-back and after the first one, i had to tilt my had almost level with the printer bottom to read the display.

I'm nearing the 16 hour mark now and the LCD is nearly completely unreadable.

If i were to guess, i'd say that either the contrast trimmer, or some resistor on the board results in such a drift in the contrast control voltage that it makes the LCD unusable after a few hours of work (and, say, 10 degrees of temperature differential).

 

Hopefully the latter, as i don't know what would cause the former.
But i won't know for sure until this run is finished and i can let it cool down completely.

This is what it looks like currently:

 

Turns out the voltage on the trim pot drifted. I'm not sure how or why, but i'm guessing it was thermal in nature.

I opened up the panel cover, readjusted it and now it's back to where and how it was.
The interesting bit is, now it takes just a micron of travel (not really, but a very very very very tiny movement) to go from "can't see anything" to "contrast perfectly fine". And no, i'm not talking normal range of a few degrees - it's an insanely small range. Just bumping the trimpot with a screwdriver will get it into the "can't see anything" zone.

Oddly, the other direction of the range is still normal.

I'd say it's a faulty trimpot and it either went "off the rails" due to thermals, or due to vibration.
Going to continue printing for a few days non-stop now i've re-set the contrast and see what happens.