Muffled Audio

I’ve been using DaVinci Resolve 16 to edit podcast audio. In random spots, the audio will become muffled for a few seconds at a time. When I go back and listen to that same audio clip again, sometimes the audio will appear normal again. It really goes in and out. When I export it, it does that same. Any tips to trouble shoot? Thank you so much!

Well this is a new one.

Starting with the basics, you're using only .wav files for source media?