Gallery 4 columns not working

I think since the last update galleries with 4 columns doesn’t work anymore, it reverts to 3 columns. Adapting the class in the html code on the page to “columns-5” does turn it into an 4 column view, but that is not possible from the page editor. It used to work, but not anymore, so I think it is a bug.

I’m having this issue on another site with the generatepress theme aswell, but not on a site using a different theme.

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