Error to generate when P-Mode can not be determined

The current text of the specification is not very clear if an error should be generated when the P-Mode can not be determined for a received message.

Questions that arise are:
1) Do we want to specify a specific Error for this situation?

2) If so, which Error should be used?

Section 6.7.1 of the Core Spec lists the standard ebMS processing errors. Based on the short descriptions it seems logical that EBMS:0010 - ProcessingModeMismatch is the correct Error to return. However the description of the semantics - "the header expected by the MSH is not compatible with the expected content, based on the associated P-Mode." - is a bit unclear because of the incompatibility between expectations and that it talks about an associated P-Mode. Especially the latter seems to suggest that a P-Mode is found for the message. Another option could be Error EBMS:0001 - ValueNotRecognized as the MSH is unable to find the P-Mode based on the received information.