Gutenberg post/page editor screen overflow

Hi guys,

When viewing Gutenberg editor post/pages, the left-side menu is overflowing into the actual post editor itself (or, rather, the post editor is overflowing _behind_ the side menu).

Please see a screenshot of the overflowing issue here: https://prnt.sc/ngg0ik
This disappears if you collapse the side menu (a workaround), but for some reason for me, this results in a gray bar being displayed across the top portion of the screen, as can be seen here: https://prnt.sc/ngg1eh