Screen recording and Audio Issue

Hello,

I'm using SL3 and the function to record a screen with Audio.

After complete the recording, i have both exported the video to MP3 and saved it as a slide.

This is where the issues crops up. When I play back the slide in preview the audio is messed up. By this I mean it starts off great but then goes quite and then loud, quite then loud.

I also checked the video export and this is of the same quality...

Please may I ask for help on how to resolve this? 

What I have done so far:

My laptop is new and all up to date

I have other audio recording software and this all works fine. example WAV: MaxxAudioPro.

My IT team have tested the mic and all is well.

 

Many thanks for you time in advance :)