When embedding a map in my MediaWiki implementation, specifying zoom 11 works as expected. Specifying 12-19 causes all map detail to disappear. I have tried changing the coordinates in case the map simply isn't detailed - no luck. I have tried making the map size bigger (changing it from 250x250 to 350x350) - no luck.
As of now, third-party usage of WMF map tile server is partially blocked due to past outage. Please take a look into https://lists.wikimedia.org/pipermail/maps-l/2020-March/001713.html for more info