Mac trying to play audio through monitor's thunderbolt port I have a Dell monitor connected through a thunderbolt port.

Sometimes my Mac for some reason is attempting to play audio through that port.  How do I stop this from happening?

It appears in my list of sound outputs in system preferences but I have headphones selected.  Unplugging the monitor from the thunderbolt port makes the audio work correctly.
Same thing happened to me. You have to manually change it in System Preferences > Sound > Output Volume.