Vega-lite: Problem with concatenation of more than two projected maps

[jwoLondon]

_(I know the team are already aware of this, but am documenting it as an issue to make tracking easier)_

If more than two projected maps are added to a concatenation, the third and any subsequent are not projected. The following minimal example shows the problem, noting that the three specs added to hconcat are identical.

{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "hconcat": [
    {
      "width": 100,
      "height": 100,
      "data": {
        "url": "data/graticule.json",
        "format": { "type": "topojson", "feature": "graticule" }
      },
      "projection": { "type": "orthographic" },
      "mark": { "type": "geoshape", "filled": false }
    },
     {
      "width": 100,
      "height": 100,
      "data": {
        "url": "data/graticule.json",
        "format": { "type": "topojson", "feature": "graticule" }
      },
      "projection": { "type": "orthographic" },
      "mark": { "type": "geoshape", "filled": false }
    },
     {
      "width": 100,
      "height": 100,
      "data": {
        "url": "data/graticule.json",
        "format": { "type": "topojson", "feature": "graticule" }
      },
      "projection": { "type": "orthographic" },
      "mark": { "type": "geoshape", "filled": false }
    }
  ]
}

[jakevdp]

I ran into this today as well.

[jimmywan]

Also ran into this problem. Any updates or suggested workaround?

[domoritz]

We haven't had time to look at this yet. If someone has time, please help us out.

[jheer]

Is this issue still an active problem? If so, I might be able to take a closer look while I work on related projection issues. (I note that it is not even flagged as a bug, but very much looks like one!)

[jwoLondon]

It remains a problem for me, so great if you were able to look at this.