Regarding the following:
<receiver typeCode="SND">
<device classCode="DEV" determinerCode="INSTANCE">
<sender typeCode="SND">
<device classCode="DEV" determinerCode="INSTANCE">
When the Message Validator checks RESPONSE messages, it flags the <receiver> typeCode attribute for not being equal to "RCV" but when checking REQUEST messages, it does not. The <receiver> typeCode attribute value must be set to "RCV" whether it's a response OR a request.