IllegalArgumentException: Invalid BSON field name uuid - mongodb

Question

So I've tried seemingly countless things to get this to work. When I call queueWrite, the println statements give me this:
{ "uuid" : "49f2-0b64-4bf3-49f2a35b-bbe8-4954f742d88b" }
and this:
{ "uuid" : "49f2-0b64-4bf3-49f2a35b-bbe8-4954f742d88b", "name" : "personName", "key" : "3E6A" }
Which (I'm pretty sure) is just fine. However, after it prints, I get this:
java.lang.IllegalArgumentException: Invalid BSON field name uuid
Afaik, the field name uuid is fine, the only things about an improper name I could really find is to just make sure there are no '.' symbols in it (which there aren't)
def queueWrite(collection: String, filter: Map[String, () => String], data: Map[String, () => String]) {
val col = collections.get(collection).get
val filterDoc = new BsonDocument
filter.foreach(f => { filterDoc append (f._1, new BsonString(f._2.apply)) })
val filterBson = Document(filterDoc)
println("filter: \n" + filterBson.toJson)
val dataDoc = new BsonDocument
data.foreach(f => { dataDoc append (f._1, new BsonString(f._2.apply)) })
val dataBson = Document(dataDoc)
println("data: \n" + dataBson.toJson)
val options = new FindOneAndUpdateOptions
options.returnDocument(ReturnDocument.AFTER)
options.upsert(true)
val observer = new Observer[Document] {
override def onSubscribe(s: Subscription) = s.request(1)
override def onNext(doc: Document) = println(doc.toJson)
override def onError(e: Throwable) = e.printStackTrace
override def onComplete = println("onComplete")
}
val observable: Observable[Document] = col.findOneAndUpdate(filterBson, dataBson, options)
observable.subscribe(observer)
}
Any ideas / suggestions are greatly appreciated as always :)