It’s a bad sign when nobody’s posted back by now.
You should be on Audacity 2.1.3 from here.
http://www.audacityteam.org/download/mac/
And then do the last Mac update. I think they fixed several streaming content and USB problems.
Here’s a thread we posted featuring “app nap” It’s a battery saving feature that you can disable for Audacity. I don’t remember anybody having trouble with it getting worse as the recording progresses, though.
https://forum.audacityteam.org/t/skipping/45947/7
Are you running out of hard drive, or are you not recording on the Mac internal drive?
Go (top of screen) > Computer > Control-click on the hard drive (Mine is Macintosh HD). > Get INFO.
Mine says 250GB memory and I have 12GB left. I would be deleting a couple of movies to get more room before I tried to record any sound performance.
I don’t know of any way to retrieve any work after the machine does that.
Koz