Line out / headphone jack quits working

I'm having a problem that is becoming more consistent. I am using my MacBook with eternal speakers attached to the line out jack. All is well. I pull the plug and insert my headphones and the system plays through the internal speaker - no sound through the headphones. I remove / reinsert to no avail. The ultimate solution varies. Sometimes I can plug the external speakers back in and they work, and then switch to headphones again. Sometimes, that doesn't work and the only solution I've found is to reboot.

I tried Rogue Ameba Soundsource per another post, but it also only sees internal speaker as an option when this occurs. Think this is bad hardware? Ideas?