Just curious Seth, are the HP's connected on the top of the console, or a HP amp on the back via XLR?
The "Studio" (XLR or 1/4") output on the back are supposed to be for the Tracking Room speakers mounted on the wall.
The "Control Room" output will mute when engaging the "Talk Back" to avoid feedback from the TB mic.
The "Studio" outs will not mute.
The "Monitor" mix would usually be whatever was send to HP cans, example - Aux 5-6 > Send to Monitor.
Or the "Merge" button on the Master section for the Tape Returns (Red knob above fodder on every channel) "Monitor Mix".
This way you can only monitor Tape Returns to Monitors if you want.