When you receive a 500 error that is coming back from WCF send port, the send port is not suspended but instead completes successfully. This is inconsistent with the behavior of this same adapter when error 400 comes back and is also inconsistent with the behavior of other HTTP-based adapters which suspend the send port instance when error 500 is sent back. This behavior also prevents you from catching the exception in the orchestration in the case of a 500 error.
This issue occurs because WCF adapters do not handle HTTP errors in the same manner as HTTP adapters do.
This problem was fixed in the following cumulative updates for BizTalk Server:
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For information about the service packs and cumulative update list for BizTalk Server, see KB 2555976: Service pack and cumulative update list for BizTalk Server.
For more information about BizTalk Server hotfixes, see KB 2003907: Information about BizTalk hotfixes and cumulative update support.