Custom Header Layouts - current column widths reset when adding a new row

[nicolepaschen]

In the Customizer I am creating a custom header layout. When I add a new row, the current row resets to 6/6 columns instead of whatever I set it at. The live preview didn't update when I tried to put the columns back where I had them. I had to close out of the Customizer and go back in before I could actually fix it.