How can I stop my Mac from automatically choosing a specific sound output device?

My Mac keeps reverting back to a certain DisplayPort option within my Sound Output settings. It's frustrating, as this port is my external monitor and renders my keyboard audio controls useless. Each time, I have to go into sound settings/output and change the selected device. I'm a professional video editor and this hiccup is causing me to lose valuable time. Is there a way to delete/hide a port from showing up, in the same way that I can tell my bluetooth settings to forget a device? SIDE NOTE: I've been using this monitor for over a year and I've never seen this happen. It's happened twice now in the last 2 days.