Re: File Path error.. Unable to post file to filepath.

I double checked the documentation on this. The SFTP documentation does not mention this explicitly, so I checked the File/FTP documentation which states below:-

Define Adapter-Specific Message Attributes

A configured variable substitution (see above) is performed after the attributes from the message header are applied.

1. To evaluate adapter attributes in the message header of the PI message, select Use Adapter-Specific Message Attributes.
2. If you want missing message attributes to trigger an error message, select Fail If Adapter-Specific Message Attributes Missing.If the indicator is set and the header for adapter-specific message attributes or one of the set attributes is missing from the message, this leads, in asynchronous cases, to a delivery exception in the audit log of the message. In synchronous cases, the sender of the message is notified.If you do not set the indicator, and message attributes are missing, the adapter accesses information from the adapter configuration

My guess is that since the SFTP adapter do not have a Fail option, it uses the default value in the adapter configuration (which is %) when the message attribute is missing.