I have the MBP 15" model 2017 (macOS High Sierra 10.13.3) with touch bar. What I realized is that the touch bar volume element (mute / unmute / volume up / down) does not work. I press them but nothing happens.
On my apple external keyboard these shortcuts work fine. Also when I try to adjust the volume with the touch bar slider it works like it should.
I tried different things, resetting nvram, removing / adding the controls, killing the control strip, killing the coreaudiod, resetted SMC. but nothing seems to fix it. The only thing that worked is opening a new user account. In the new user account everything seems to be working fine.
Any ideas of what the problem might be or how it can be fixed?