When was it changed?
Hmm, the only thing I could advise is get it booked in at Audi as their diagnostic machine is more in-depth. Plus they'll be able to do the software update.
Can't say I've heard of other cases, however this cannot be a wear and tear issue when the components shouldn't break away like that. It's definitely a fire risk.
I'd recommend a diagnostic check to see if any fault codes flag up as it could be an issue with the heater control unit. However, does the engine get up to temperature ok? As I believe a failing thermostat can cause similar problems.