I have a BV Avant with a BeoCenter 2.

On the AUX of the BC2 I have a old turntable. With my beo4 can select it with A.AUX.
On the Beo5 this switches on the Radio. The code send is:

0:000:RADIO:AUX_A

Has anyone an idea?
 

Did you ever try to use PHONO instead of A.AUX? My ouverture is accepting both commands to switch to the AUX input.

I had a similar problem as you. Try to create a new button, do not use the one that was created with your set up (delete it)

I, too, had a similar problem. In my case, I kept the same button but changed the label of the button to "turntable" and it worked. This makes no sense, but it worked.