Biztalk FILE Send Port throws "The system cannot find the file specified"

If you receive this exception in BizTalk

A message sent to adapter "FILE" on send port "SENDPORT_FILE" with URI "\\ABC\PATH\%MessageID%.xml" is suspended. 
Error details: The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
MessageId:  {5EC92559-C6E3-490C-A1D4-981D154BA126}
InstanceID: {4FF0F3DE-9A4C-4ECE-8C5A-98B34C78701E}

the reason could be that BizTalk does not find the assembly during runtime in the GAC, although it was there. In my case, I had to create the assembly in Development mode instead of instead of and then BizTalk could find the assembly.

SAP WCF MetadataException "RFC IDOC_INBOUND_ASYNCHRONOUSM could not be resolved against SAP"

If you run into this error

The adapter "WCF-Custom" raised an error message. Details "Microsoft.ServiceModel.Channels.Common.MetadataException: RFC IDOC_INBOUND_ASYNCHRONOUSM could not be resolved against SAP system because its metadata could not be obtained. ---> Microsoft.Adapters.SAP.RFCException: Details: ErrorCode=RFC_EXCEPTION. ErrorGroup=RFC_ERROR_APPLICATION_EXCEPTION. SapErrorMessage=FU_NOT_FOUND.  AdapterErrorMessage=An error occurred while determining the function interface of the RFC IDOC_INBOUND_ASYNCHRONOUSM.

then you might use a the new WCF SAP adapter with a Non-Unicode RFC Destination. The BizTalk Adapter Pack 2013 does not seem to be compatible with Non-Unicode RFC as it was before. The only solution seems to be to create a new RFC Destination in SAP.

WCF SAP Exception ArgumentNullException "Value cannot be null."

If you run into this error:

The adapter failed to transmit message going to send port "SAP_NokasPettyCashImport.SendToSap" with URL "sap://CLIENT=007;LANG=EN;@A/XXX/00?GWSERV=XXX&RfcSdkTrace=True&AbapDebug=False". It will be retransmitted after the retry interval specified for this Send Port. Details:"System.ArgumentNullException: Value cannot be null.
Parameter name: key

....check whether you really put in an Action in the WCF SAP Sendport (or the Action property arrived at the Sendport).

BizTalk Adapter Pack Updates

Just to not forget: Microsoft has a useful list of all updates concerning BizTalk. Please do not forget (like it happened to me) to scroll down until you reach the BizTalk Adapter Pack updates. They are published separately.

Please open the BizTalk Update Site with Firefox - I'm not joking, IE 10 was hiding the Adapter Pack 2013 updates due to an html error.