e.g. [[ https://wikiapiary.com/wiki/Wikipedia_(en) ]]: click "General" and you'll see most of the fields are blank, the "MediaWiki Version" field has a SMW error, and there's a big mess of code at the bottom. This is caused by nested `{}` in the `pageviewservice-supported-metrics` parameter on [Website]/General (e.g. for "Wikipedia (en)", the value is `{u'siteviews': {u'uniques': u'', u'pageviews': u''}, u'mostviewed': {u'pageviews': u''}, u'pageviews': {u'pageviews': u''}}`; note the `}}` at the end).
In addition to `pageviewservice-supported-metrics`, this could potentially also affect the `readinglists-config`, `galleryoptions`, `linter`, `imagelimits`, `wmf-config`, and `magiclinks` parameters, so any fix should also apply to them (if possible, it might be best to just apply it to all parameters).