Mac mini will stop being able to stream media (video or audio)

My 2012 Mac mini recently developed an odd problem where it will suddenly stop being able to stream any kind of media, be it video on Twitter or YouTube, or audio through the Spotify app or website.

Video will stop working on Safari, Opera, and Chrome alike. (Don't remember if Music.app will or won't stream my iTunes Match songs, will try that next time the problem starts.)

I'm stuck as to how to isolate the problem, but I've noticed a few things.

• A reboot will get it working again, for a while, a day or longer.
• When the problem happens, it happens across all accounts on the computer.
• Videos, even though they won't play, can often be scrubbed through by moving the playhead back and forth.
• Video and audio stored on a hard drive, internal or external, will still play normally.

I'm hopeful that someone who had a similar problem found out how to fix it and can help a fellow out!