DTL Transformation output: ordering of XML nodes

We are using a DTL transformation to take HL7 and transform into custom XML. But the nodes in the resulting XML are appearing out of sequence - and therefore failing validation against the schema.

The XSD schema for the XML looks fine when imported into Ensemble: root node in the XSD looks like this:

And shows in Ensemble like this:

The transformation looks like this, and we can see the text from the trace elements at lines 5, 12 and 19 appear in the correct order in the event log:

HOWEVER, the resulting XML has the <allergies> nodes before the <patientNotes> nodes....:

Any ideas about why this is happening, and how we can ensure nodes are generated in the correct order?