you may recall a thread where I spilled coffee on mine. the malfunctions are related to the spilt liquid creating a short circuit. This fault actually gets logged in the computers somewhere according to Audi Tech.

Mine seemed to get worse when it was cold as the return button would stick. After pulling and cleaning the buttons, it has been fine. To be fair, I did not spill much liquid on it. I think if you spilt a whole cup, the unit would be dead. If it still works, its 50:50 whether a clean will fix it, but its worth the shot.

You can take the unit out, strip it down and clean it with electrical contact cleaner. Makes it like brand new again. If you Google "coffee spilled on my mac", you get a guide on how to clean out electronics.

A new unit is £700 when I asked last time. Taking the thing out takes about 30 minutes as you need to strip down the centre console