Scroll bar is missing when editing posts

The scroll bar is missing when editing posts on one of my subsites. You can check on the post: https://troymedia.com/business/entrepreneurship/the-lone-wolf-business-entrepreneur-is-a-dangerous-myth/
From my developer:
I couldn’t find an option to edit the scroll behavior. I also tried to force the scroll with CSS attributes like overflow-y: scroll, but it gets immediately reverted once we interact with the editor interface, which is an iframe.

The behavior seems intentional, and the scroll works for the full page while keeping the top menu visible with sticky effects. I was able to access any element in the editor without issues, so the scroll behavior is not preventing the edit functionality.

The page I need help with: [log in to see the link]