It is strongly recommended that you Export WAV safety copies of all original work just to avoid this problem. If your processing or editing turns to peanut butter, you can just trash it all and open up the protection copy.
WAV is an uncompressed format and essentially perfect. You know when you picked the compression quality for your MP3? 128, 320, etc? Stereo WAV quality is 1400.
Do that at the other end, too. When you get your final edit, export it as Final Archive WAV. Only Then make the MP3 for ACX audiobook posting.
ACX wants submission in 192 quality MP3 (minimum) and they strongly recommend mono (one blue wave) over stereo.
We posted one method of audiobook mastering.
https://forum.audacityteam.org/t/audiobook-mastering-version-4/45908/1
Which one are you using and is it working for you?
Koz