Masonry gallery single column

When I am in the post itself (in this case https://gutenpage.com/blocks-gallery/ ) then the blocks shows the images correctly – two across.

When I am in the site but not in the specific post, then the images show in a single column.

I cannot recall whether this was an issue before WP 5.0 and the latest version (Version 1.1.2) of the plugin.

I switched them to TwentyNineteen in case it was a theme issue, but it displays the same way.

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