TV's need to be correct case

This is something I might look at fixing myself, but essentially if you enter a Tv Type with incorrect capitalisation (which is somewhat inconsistent throughout modx) you get possible errors with duplicate output renderers, all tv types need to be sanitised when they're coming from the JSON file

Is this confirmed as the problem you were having in Issue 15?

Perhaps just simply making the type lowercase would be enough e.g.

if ($property === 'type')
{
    $element->set($property, strtolower($value));
}

or do some types require capitalisation?