I recently reset my computer, and in the process I lost my old Shotcut app (from about mid-2018). When I downloaded a more recent version, the sound during editing was horrendous (distorted, crackling, halting), making the program unusable. I’ve never before had any audio issue of any kind with any application on my computer. I tried everything to correct this problem, including uninstalling and reinstalling Shotcut, trying half a dozen older versions of the program, installing new audio and other drivers on my computer, and cleaning the disk drive. Nothing worked for any length of time, just for very brief periods on two occasions. Finally, playing around with the settings after installing the very latest version, I discovered that changing the Audio Channels setting from 2 (stereo) to 6 (5.1) did the trick. It’s been a while now since I did this, and there has been no problem whatsoever with the audio during editing. It looks like the good sound is here to stay. (During the time I was dealing with this issue I gave up on Shotcut altogether and switched to DaVinci Resolve. But, ironically, the sound quality of the exported, final videos in DaVinci is inferior to that of Shotcut, which has always been perfect despite the editing sound problem.)
Just now I Reset the User Interface in Settings (for an unrelated reason), and the bad sound returned. I then changed the Audio Channels setting from 2 to 6 and the audio problem disappeared once again. So, short of fixing the bug, that is clearly the solution.