ACK being assembled with wrong MSH values

[Jeff Wessling]

Hello, I hope someone can help me with this issue.

I recently inherited a Biztalk HL7 solution and am trying to support
it. Recently a issue has come up where an ACK is being sent that
appears to have all the correct values in it's XML form, but when it
is assembled by the BTAHL72XSendPipeline different values are being
used for the MSH segment. Samples are below (both show only the MSH
not the MSA, and have had the send and receive ids deidentified) :

XML:
<ns0:MSH_25_GLO_DEF xmlns:ns0="http://microsoft.com/HealthCare/
HL7/2X">
<MSH>
<MSH.2_EncodingCharacters>^~\&amp;</MSH.2_EncodingCharacters>
<MSH.3_SendingApplication>
<HD.0_NamespaceId>XXX1</HD.0_NamespaceId>
</MSH.3_SendingApplication>
<MSH.4_SendingFacility>
<HD.0_NamespaceId>005</HD.0_NamespaceId>
</MSH.4_SendingFacility>
<MSH.5_ReceivingApplication>
<HD.0_NamespaceId>YYY</HD.0_NamespaceId>
</MSH.5_ReceivingApplication>
<MSH.6_ReceivingFacility>
<HD.0_NamespaceId>005</HD.0_NamespaceId>
</MSH.6_ReceivingFacility>
<MSH.7_DateTimeOfMessage>
<TS.1>20110112125628</TS.1>
</MSH.7_DateTimeOfMessage>
<MSH.8_Security/>
<MSH.9_MessageType>
<CM_MSG.0_MessageType>ACK</CM_MSG.0_MessageType>
<CM_MSG.1_TriggerEvent>R01</CM_MSG.1_TriggerEvent>
<CM_MSG.2_MessageStructure>ACK</CM_MSG.2_MessageStructure>
</MSH.9_MessageType>
<MSH.10_MessageControlId>123456</MSH.10_MessageControlId>
<MSH.11_ProcessingId>
<PT.0_ProcessingId>P</PT.0_ProcessingId>
</MSH.11_ProcessingId>
<MSH.12_VersionId>
<VID_0_VersionId>2.2</VID_0_VersionId>
</MSH.12_VersionId>
</MSH>
</ns0:MSH_25_GLO_DEF>

HL7:
MSH|^~\&|XXX2|001|YYY|001|20110112125628||ACK^R01^ACK|123456|P|2.2

I can see from BizTalk tracking that the XML is received with the
right ids, but the assembled HL7 uses different ones. I've got a good
amount of BizTalk exp, but am lighter with regards to working with it
and HL7. Is there a trading partner association I'm missing, or some
default identifiers that are used in some cases?

Making this issue even more odd is that it only happens with ORU^R01
messages, ADTs are assembled and send back with the appropriate
identifiers.

Thanks, any help is appreicated.