Expanding the comment options causes page to expand

Hello,

I'm a new WPDiscuz user and have noticed something strange. 

When I'm on mobile and I click the "join the discussion" box to expand the name, email, and code fields, the width of the page expands on the right side. (see screenshot).

This only seems to happen on mobile and only when clicking on that box (if you don't click on it to expand the fields then the width is fine).

I'm using Generatepress.

Any ideas?