I know this is an ancient question, but I'll share what I just learned on same unit which has been in place for 17 years...
I had a situation where the buttons were getting harder to operate then one of the zones no longer worked properly. For example, if "Boost" were pressed the light would come on for a few seconds and then go off, the entire LCD panel disappearing as it did so.
Having read about batteries needing replaced, I checked that out first but it was good. Then I noticed the buttons were, despite plastic covers, actually just silicone with conductive paint applied. This is a real cheap way of doing buttons and the paint rubs off with time. Using "Remote Restore" paint I renewed the paint dots (19 in all (6 per zone plus 1 for the mode selector) and it was fine again.
NB - wrestling the unit off the wall was a tough job. The back-plate is about 60% of the unit width and the unit needs prised of off this using something thin and strong (think more like a pallate knife than a screwdriver)
Squealy, September 2023
