Q: Macbook pro has intermittent audio when watching video

My daughter's 2012 MB Pro has intermittent audio problems (speakers or earphones). We notice this more when watching Netflix. We have audio at first and then it goes away. We've seen a red light flash at times in the headphones jack but don't know if this has anything to do with the issue. When I run system preferences, normal hardware is identified but when we are having this problem, a digital setting but no speakers show. The laptop is running Yosemite and has had this problem on and off for some time.

I'm guessing we have a software incompatibility but would like to know if others have seen and fixed this problem?

Thanks, Dale