JSONFragmenter returns json_type = object instead of json_polygon

Hello,

Can someone explain to me why is JSONFragmenter returning json_type = object instead of json_polygon? And how to adjust anything to get valid json_polygon?

Parameters of JSONFragmenter:

JSONFragmenter returns:

Usually for this kind of JSON data I get (with correct geometry):

JSON data for correct return is given as attachment, as well as the incorect one.