Upserting on embedded document - mongodb

Question

I have the following document strucutre
{
"_id" : "NmBYYasdsa",
"objectId" : "asdsd"
"text" : "test",
....
"publishedAt" : ISODate("2015-05-28T15:31:51Z"),
"updatedAt" : ISODate("2015-05-28T15:31:51Z"),
"data" : {
.....
"likeCount" : 0,
"replyCount" : 0
}
}
That is use to synchronise my database with an external API. To do this, I poll the API once every minute and do a bulk upsert, matching on the object id to keep my database up to date.
Problem is that the data subdocument doesn't get updated when upserting, any ideas as to why?
My bulkwrite method
Mongo.Collection.prototype.upsertBulk = function(matcher, documents, options) {
if (_.isEmpty(documents)) { throw Error('Empty list of documents provided'); }
options = options || {};
var operations = documents.map(function(_document) {
_document._id = Random.id();
var operation = {
updateOne: {
filter: {},
update: { $set: _document },
upsert: true
},
};
operation['updateOne']['filter'][matcher] = _document[matcher];
return operation;
});
this.__mongoCollection(function(collection) {
collection.bulkWrite(operations, options, function(error, result) {
if (error) { throw error; }
return result;
});
});
};