[nednednerb]

Sometimes Headphone output is different from Speaker output.

Sometimes, apps can switch. Sometimes they cannot.

Sometimes an app connects the two and allows easy switching. Something might have changed, and it isn't on that "setting" any more.

How are you using the app? How are you switching? I would totally expect crash or something if I starting unplugging wires mid session... Do you know that you should set it up, stick with a session, and not expect simple fast "plug and play" with a bunch of devices at same time? At any rate, I would suggest slowing down and knowing which audio device Pro Tools is currently set on, and be mindful if other devices/apps are trying to be active.

I mean by "audio interface" NOT the headphone jack.