rally-node Add new item to collection

Using the rally-node toolkit, I'm getting an error message returned when attempting to add new Changeset, with new Changes inline, to an existing Userstory. When I have the new Changes commented out there's the Changeset is added as expected. It seems to be something specifically with the Change data that I can't figure out.

Add call:

rallyApi.add({  
  "ref":"https://rally1.rallydev.com/slm/webservice/v2.0/hierarchicalrequirement/91834286580",
  "collection":"Changesets",
  "data":[  
    {  
      "Author":{  
        "_ref":"https://rally1.rallydev.com/slm/webservice/v2.0/user/53634054872"
      },
      "CommitTimestamp":"2017-03-17T09:52:07-04:00",
      "Message":"Feature/tags (#11)",
      "Revision":"b8460460254cb79d3e72c98172c164f5c4d3493a",
      "Uri":"https://ghe/org/repo/commit/b8460460254cb79d3e72c98172c164f5c4d3493a",
      "Changes":[
        {
          "Action":"M",
          "PathAndFilename":"file1.json",
          "Uri":"https://ghe/org/repo/commit/b8460460254cb79d3e72c98172c164f5c4d3493a/file1.json"
        },
        {
          "Action":"M",
          "PathAndFilename":"file2.json",
          "Uri":"https://ghe/org/repo/commit/b8460460254cb79d3e72c98172c164f5c4d3493a/file2.json"
        }
      ],
      "SCMRepository":{
  "_ref":"https://rally1.rallydev.com/slm/webservice/v2.0/scmrepository/101417587520"
      }
    }
  ]
})

Returned error: { [Error: Could not create artifact to collection] errors: [ 'Could not create artifact to collection', 'Cannot parse object reference from "{null: {"Action": "M", "PathAndFilename": "file1.json", "Uri": "https://ghe/org/repo/commit/b8460460254cb79d3e72c98172c164f5c4d3493a/file1.json"}}"' ] }

It seems to be telling me it tried to find an existing change with that data, but I want to add a new change as specified in the docs and a recent question:

https://github.com/RallyTools/rally-node/wiki/User-Guide#add-to-a-collection

Rally API Add Tags to existing userstory NodeJS

via Matt Murphy