a50 - Loose sound when trying to adjust volumne

Hi there.

I have the a50s. When I try to adjust the sound, whether up or down, I will loose all sound. I try to adjust the volume up and nothing happens. Sometimes I have to scroll the volume wheel up continuously for an extended amount of time (30 sec or more of trying to turn up the volume) before I get any sound.
I just updated firmware (15 Oct 16) and it still does the same thing. Any help will be appreciated.
Thanks