Two column layout: 1 fixed, 1 scrolling

Site URL: https://anxioussound.com/aoty-2021

Hello,

I'm using the Foster template in Squarespace 7 and I'm trying to create a two-column layout where the left column is fixed (non-scrolling) and 100vh, and the right column is scrollable. 

I was able to get the layout I want in the editor by creating a new fixed code block and positioning it to the left of all other content (top image). The problem is, as I soon as I save the layout and leave the editing state, the content in the right column jumps to the left, overlapping with the fixed column (bottom image).

Why does the layout change when I leave the editor? Is there something I'm overlooking in the code? 

Fixed. I had to re-position the fixed left column code block in the editor so that it wasn't to the left of all the other blocks (the right column) but above them. I then set the width and margin-left declarations for the .Main-content element to 50%.