Some VT geometries have duplicate rings

[mourner]

While investigating shape triangulation for Mapbox GL JS, I discovered a really weird bug: some shapes in VT that are supposed to have one ring of vertices actually return several duplicated rings. I mean, instead of [ring] it has [ring, ring, ring] in the data, where ring is an array of coordinates.

Not sure if it's a Mapnik VT issue, data issue, vector-tile-js or anything else. Any ideas will be appreciated.

One particular example in http://b.tiles.mapbox.com/v4/mapbox.mapbox-streets-v6-dev/15/9370/12535.vector.pbf

The green park around the Embassy of Saudi Arabia in DC is returning 3 rings instead of one.

cc @yhahn @springmeyer

[mourner]

I'm sorry, this turned out to be a JS issue on our side.