I don't have a solution, but I do know that quite a few YouTubers use a seperate program to record their microphone audio.
Perhaps considering an alternative may help.

I'm having the same issue. 1920x1080p is my native resolution, yet when I record in that size the playback has black bars down either side of the screen. I assumed it to be a trial version feature like the watermark that will change, if I purchased the product. But because I'm experiencing this issu...