VS-KRThere isnt any problem with button, i have checked that through .12345+= method, its a pass. its purely a software bug.
We need to know if the button is dead or if there is something wrong in the software.
To check the first idea, go to Parameters, Assistance, Examination/Check, Test keys.
You'll have to press Volume +, Volume - and Smart Key.
If you pass the exam, then something is wrong between Smart key and the software, but the button is still alive.
*The procedure is also available with the .12345+= method.