@Lucie Is this something you could look into?

The tours are missing https://doc.wikimedia.org/mediawiki-core/master/js/#!/api/mw.Api.plugin.edit-method-postWithEditToken because the module is not loaded by https://www.wikidata.org/wiki/MediaWiki:Guidedtour-lib.js .

We figured you'd have to replace the function removeData() in the MediaWiki:Guidedtour-lib.js with

	function removeData( tourName, newData ) {
		mw.loader.using( 'mediawiki.api.edit', function() {
 
			new mw.Api()
			.postWithEditToken( {
				action: 'wbeditentity',
				id: mw.config.get( 'wbEntityId' ),
				clear: true,
				data: JSON.stringify( newData ),
				summary: 'Clearing data for [[Wikidata:Tours#' + tourName + '|' + tourName + ']] tour'
			} )
			.done( function() {
				location.href += '&data=ok';
			} );
		});
	}

so the module mediawiki.api.edit is loaded, which is needed for .postWithEditToken.
Might not be the whole solution but at least we will be able to see the tour at all and can see how to proceed from there.
I don't have the necessary rights to change the page on Wikidata, so if someone could have a look into it would be great!

Bene* fixed them. I had a look on it and they seem to work properly again now.