Why don't the buttons on my IHD3 device work?

My IHD3 device has been clearly measuring energy usage, but at times it has been ‘beeping’ for no reason that I can establish. When physically investigating the device none of the buttons worked at all. Has anyone got any suggestions?

Mine does this, I find unplugging it and waiting for it to turn off helps.

Turn it back on and it should be working again