[abovetherim]

I had one of the digits not reading correctly as 1 or 2 of the bars remained permanently lit. I removed and opened the unit up, not that difficult to do hoping to find a loose or bad solder joint. I couldn't find the issue as with mine I think it may have been a component failure and i'm not that good with electronics to diagnose what.

But.....
If i recall correctly the display is connected to the main control board with a ribbon connector. This could be where your problem may be though it could be a component failure in a capacitor (will be obviously leaked or bulging) or a transistor.