I don’t think this is it, but I can see one mismatch. You have the Mac microphone set to record mono and yet you have a stereo (two blue waves) show.
It’s good practice to export all your original sound and performances as WAV 16-bit, 44100 sound files before you start editing and edit a copy. Saving an Audacity Project is not recommended for this.
If you’re cutting your original performance and Audacity goes into the mud, it might take the original recording with it.