Columns in Firefox show bottom section in its own section

I can only replicate this issue in Firefox.

Steps to replicate:

On a new lessons tool, create 8 subpages all from the main Lessons page.

Select the column properties button on the top left of Lessons

Select the box for "Two columns inside this one, text flows between them

Save

Select edit text on one of the subpages, close the edit item popup box.

The edit options for the last subpage are now displayed below the subpages in its own section(See screenshot).