Please see this post https://forum.audacityteam.org/t/crackling-audio-playback-multiple-formats-and-volume-level/31325/2 . Let us know the answers to those questions in your case and see if any suggestions in that topic help the problem.
Since we don’t know the exact three-section version number of Audacity that you have, I also suggest you try the 2.0.5 release candidate here: https://forum.audacityteam.org/t/audacity-2-0-5-release-candidate-2-available-for-testing/31389/1 .
I doubt preferences reset will help unless you are using very unusual sample rates in Audacity, but first of all, Audacity > Quit Audacity. To find audacity.cfg, open Finder, Go > Go to Folder and type:
~/Library/Application Support/audacity/
then delete audacity.cfg.
If you have (or have ever had) 1.2 on your system, you will also have to go to:
~/Library/Preferences/
and delete the file called “audacity Preferences”.
You could also use Go > Utilities > Disk Utility and run “Verify Disk”.
Gale