Zoom buttons do not appear in some maps. The "maximize component" button looks slightly off too. See:
Note that in the Show preview it looks fine. Wikivoyage maps look fine as well (https://en.wikivoyage.org/wiki/Barcelona).
@MaxSem: That's well outside my expertise... could you have a look if you have time? Thanks!
I think this is intented for Wikipedias with static maps instead of dynamic maps. The zoom buttons appear expanding the map or in preview, not in read mode as the page is cached with a static map.
Anyway, the full screen button looks more wide in Wikipedia than in Wikivoyage.
Oh, that makes sense, I'm sorry I didn't think about that. If someone can confirm this, this task should be closed and maybe splitted into two "minor" tasks: one about the full screen button and another about the show preview page.
By the way, the "full screen" button could as well disappear for static maps in my opinion, we don't have a full screen button in images.
On Wikivoyage: <a class="mw-kartographer-map mw-kartographer-interactive leaflet-container leaflet-retina leaflet-fade-anim">.
On Wikipedia: <a class="mw-kartographer-map mw-kartographer-link">.
See your web browser's developer tools. :)