The sound distorts like hell

Please kindly follow the below two steps to improve this.
1. You could have a check whether the firmware of the camera is updated to the latest version.
2. In order to estimate whether the files is damaged by the sound, you could turn off the video and audio, and then record another one.
There are two options for audio mode: stereo and human voice enhancement (HM). You could switch to HM mode to record a piece of video.