Video audio adjusts automatically

I have an iPhone 11 and recently the volume of the audio when recording videos using the apple camera app adjusts automatically. In playback, the audio is very quiet and within a few seconds adjusts to being loud. It’s like an automatic fade in for the video. This is occurring when recording videos playing fingerstyle acoustic guitar and the front facing camera. I have not tried the other camera. I’ve searched many forums and tried the basic options to fix (ex. Software update, restart, turn off record in stereo). I’d like to know if anyone else is experiencing the issue and knows how to turn off this option. I haven’t tried exporting the video to another device and observing the playback meaning perhaps it could be an issue of playback on the phone (ear protection) rather than the recording process?