Instance completed without consuming it's messages

Question

Hi, I'm new to BizTalk and am having trouble with a simple Orchestration I am trying to build.
I'm looking to receive a flat file which could contain multiple orders and am debatching it in the Pipeline.  I then have an Orchestration which receives this message, recombines it with the File Header and will then transform the message a couple of
times to produce the final message which is sent out.  I have tested the orchestration can combine the message correctly (the Construct Single Order shape) and with a Send shape straight after it works fine.  However whenever I add an additional
transform shape (ConstructMessage_1) the Orchestration fails with the message 'The instance completed without consuming all of its messages. The instance and its unconsumed messages have been suspended.'  To be clear this occurs even when the input file
has only one order and therefore only one message is processed.
I've tried numerous combinations of the position of the second transform and cannot get this to work (the final solution will have a number of Decide shapes to determine which transforms to run). I am sure there is something very simple I'm missing and would
appreciate your help.  
I can't post images at the moment but will post one of the orchestration as soon as I am able, sequence of shapes is below
Receive Shape - receives debatched message
Construct Message Shape - ConstructSingleOrder, containing
  - Message Assignment (where I retrieve the Header information from the debatched message and assign it to a message)
  - Transform Shape (where I map the Header message and the body message into a single message)
Then I have another Construct message shape (ConstructMessage_1) containing a single Transform shape)
Finally a Send shape

Answer 1

As a final note, I have managed a work-around.  It doesn't feel very elegant due to the simplicity of the Orchestration I building but I came to the conclusion that the code to pull out the file header information and combine it with the debatched order
//put header data into string variable
stringVariable = DebatchedMessage(XMLNORM.FlatFileHeaderDocument);
//create XmlDocument from string variable
xmlDocumentVariable = new System.Xml.XmlDocument();
xmlDocumentVariable .LoadXml(stringVariable);
//assign message from xml document
HeaderMessage = xmlDocumentVariable;
doesn't play well with other shapes so have given this it's own orchestration with a Direct Bound port linking it to the next orchestration where I do my conditional mapping.
With the above change it is now managing messages successfully, thanks for your assistance in trying to resolve this.