Author Changing Post Format

Hi everyone, I’m hoping that someone may be able to help me with a formatting issue that I’ve come across.

When I change the Author on a post to a new Author that I’ve just added (the second on the website) the format of the post changes to include the sidebar on the right of the page and also surrounds the content in a grey box. All other settings are the same. I’ve also checked this on old posts and changing the Author has the same effect.

I’m using WordPress and Elementor. I’m using the Quick Edit feature on the WordPress Posts page to change the Author and that’s the only thing that’s changing to cause the formatting issue.

Does anyone have any ideas of how I can resolve this/keep the formatting same as it would be using the other Author? I’ve tried recreating the second user profile but that hasn’t helped.

Any suggestions would be much appreciated!