Form block dropdown menu: down arrow misplaced

The little down arrow that indicates the dropdown field is always misplaced on my page, it is right below the field. But it should be inside the field.

Strangely, it’s all fine in the editor. I tried deactivating all plugins except Jetpack, tried another default theme, no change. (We are using Twenty Twenty-Four but it’s the same with Twenty Twenty-Three or others.)

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