The behaviour with the audio buttons flashing may be caused by a midi driver on the Mac called the IAC Midi Driver.
I suggest that they disable it to see if it solves the problem.
To disable this driver search for 'midi' in your Mac's spotlight search and then have a look in the settings of the Audio MIDI setup. When in the Audio MIDI setup if you go to 'window', 'show midi studio' and then click on 'IAC driver' and 'show info' a window should come up for the IAC driver. If 'device is online' is ticked then untick it and the IAC Midi driver should now be disabled.