Had our Fox T2 for years and around 5 years ago replaced the handset as the buttons were unresponsive. The 2nd handset fell over on me today, all of a sudden. Battery change not effective.
I still had the original handset so after looking at https://myhumax.org/forum/topic/how-to-open-up-and-clean-remoterm-f01-control I took it apart and cleaned it, using RS contacts cleaner/lubricator. Now works. I cleaned considerable dirt off the rubber contacts; the PCB surfaces were reasonably clean.
Whilst learning the trick of separating the top and bottom of the handset via some Youtube videos, I came across one video suggesting you tried a different trick first. This was to remove the batteries, then hold down the On/Off button for at least a minute, then press each of the other keys several times. Before taking the "new" handset apart to clean it (thus providing his and hers handsets 
), I tried this trick .... and it worked, without needing the handset to be cleaned!
Now this feels like a discharge of static or other charge, which would perhaps explain why the more recent handset suddenly went from fine to non-working, on pretty much all keys at the same time. And if you take it apart and clean it, you're probably also discharging any static.
So, perhaps if you've a u/s handset, try that first.
Does anyone know what the technical descripiton is of the type keys in these handsets? The rubber keys look like rubber alone, with no coating, so I am surmising a capacitance sensor of some description.
