Both on German and English Wikivoyage branches you can look for pages which are linked to the mapframe template to find examples for check.

Normally, wgKartographerMapServer is a global variable set to https://maps.wikimedia.org (defined in Kartographer/extension.json). I do not know why the wgKartographerMapServer variable is missing.

On my Android smartphone with Chrome 67.0, I can switch the mapframe to full screen, but sometimes there are no icons on the full screen view.

At German Wikivoyage we are using an additional JavaScript library, https://de.wikivoyage.org/wiki/MediaWiki:MapTools.js, which is calling ext.kartographer.box in a manner as described in the documentation. I switched it off, and the runtime error/exception occurred furthermore.

The config variables like wgKartographerMapServer are not set in the document header. I think they will be set by the ResourceLoader because they are noted only in extension.json.

"config": {
	"KartographerStaticMapframe": false,
	"KartographerWikivoyageMode": false,
	"KartographerDfltStyle": "osm-intl",
	"KartographerStyles": ["osm-intl", "osm"],
	"KartographerSrcsetScales": [1.3, 1.5, 2, 2.6, 3],
	"KartographerMapServer": "https://maps.wikimedia.org",
	"KartographerIconServer": "https://maps.wikimedia.org",
	"KartographerFrameMode": "interactive",
	"KartographerUseMarkerStyle": false,
	"KartographerEnableMapFrame": true
},

The JavaScript (for the mapframe map, too) is performed "on load" (on ready). It seems that the variables needed are not available at this time.

If such a runtime error occur then the folowing loader functions fail:

mw.loader.using( [ 'ext.kartographer.box' ] ).then( function() { ... } );
  or
mw.loader.using( [ 'ext.kartographer.box' ] ).done( function() {
  /* This callback is invoked as soon as the modules are available. */
} );

ie the callback function will never be called.

wgKartographerMapServer is provided by module ext.kartographer, which is a dependency of ext.kartographer.box, but is not a dependency of ext.kartographer.settings. That seems like a mistake in the RL definitions indeed.

At the travellers' pub at the English Wikivoyage edition another fault scenario was reported: If now zoom parameter is set (auto-zoom mode) a world map is displayed instead of a location map. It seems that the runtime error explained prevents the calculation of map center and zoom.

If no zoom parameter should read instead of If now zoom parameter.

As @TheDJ found, this is not a problem with ResourceLoader framework or its logic. The Kartographer seems to be missing an implicit dependency between two of of its modules.

Change 449619 had a related patch set uploaded (by TheDJ; owner: TheDJ):
[mediawiki/extensions/Kartographer@master] Fix Exception in ext.kartographer.settings module

https://gerrit.wikimedia.org/r/449619

Change 449619 merged by jenkins-bot:
[mediawiki/extensions/Kartographer@master] Fix Exception in ext.kartographer.settings module

https://gerrit.wikimedia.org/r/449619