Ongoing, intermittent issue: (specs at bottom of comment)

I primarily have my sound coming through the 27 inch display. For the most part, it works fine. As I'm watching something on youtube (or hulu, or other), the sound will break once or twice for a second... . about 30 sec – 1 min later, the sound will stop. The video is still playing.

My current remedy (and possible marker toward the issue) is to unplug the 27" USB connection for about 10-30 sec. During that time the sound will often revert to the 24" monitor. Occasionally, the sound will be out of sync from the video.

When I plug the 27" USB back into the laptop, the sound returns & usually stays.

See system specs below

MacBook Pro (Retina, 13-inch, Early 2015)

3.1 GHz Intel Core i7

16 GB 1867 MHz DDR3

Intel Iris Graphics 6100 1536 MB

2 (non thunderbolt) Apple Cinema Displays connected through 2 thunderbolt ports

also have them connected via USB.

Display 1: 27" Apple Cinema Display

Display 2: 24" Apple Cinema Display