A whole bunch of years later I'm experiencing the same problem. No matter how I export the video, spoken word is clipped and disgusting, barely understandable. Mind you this is audio track linked to the video, recorded with GoPro h265. Original audio quality, and the preview playback are both perfectly fine, the issues is just with exported video and this started to happen with the update to version 7.32 and "Automatically normalize audio volume" in the Settings/Media is disabled. I tried exporting it with default settings and also with the highest bitrate on both h264 and mpeg4, nothing changed. (Note that exporting to h265 doesn't work at all.)