Audio in my 135 ('09 also) went out about 5 weeks ago. First time I returned to dealer (LB BMW) and, of course, radio worked when I started the car for the SA.
A few days later, it went out again and SA witnessed condition. After having car for 2 days, SA said basically same thing - known problem, software fix in works, ... s/w update s/b avaialble in month or so...
Based on the feedback you received re: s/w availability schedule, will call them in early June.
Good thing the motor plays such sweet music
!
c1