MMI source /aux options missing (sometimes)

First Audi and first post here so hi!

Just purchased a A6 2006 3.0 TDI S Line Quattro Avant loving the car, so far only one small niggle with it...every once in a while the MMI does not show options for the CD Changer or the Source Options (aux in). Source normally displays:

01 - DVD
02 -DVB
03 - AUX1
03 - AUX 2

The MMI will select the Source menu and the Changer but they are empty, to resolve I have to restart car / MMI a couple of times and the options reappear . When its playing up Radio works fine.

The car has SAT NAV , 6 Disc Changer and Bluetooth and I think its the 2G MMI not up on the technical side of Audi terminology yet. From the previous owner I gather the AUX in's were retrofitted and he also at one point had DVD and rear screens that were wired for sound MMI.

The issue has happened 3 times in the last week, any ideas on why and a solution ?

Only got Torque app on my phone at the moment and that does not cover any of the modules other than the engine one. Looking at VAG COM there seems a lot of them on ebay any particular vershion and cable I need to be looking out for?

What is the current firmware version?