When a node is passed as the context item to the JAXP XPath evaluation APIs, Saxon needs to check that the NamePool used when building the document containing the node is the same as the NamePool used when compiling the XPath expression. This check is being performed correctly when the object passed is a Saxon NodeInfo, but is omitted when the object is a NodeOverNodeInfo, that is, a wrapper object that presents a DOM interface to a Saxon node. The consequence of using inconsistent namepools is unpredictable; it may result in exceptions reporting invalid name codes, or it may simply cause the XPath expression to deliver incorrect results. A patch is being added to Subversion on the 9.2 branch to detect and report the error.
(Apologies, by the way, for the bad word-wrapping on these bug entries. The problem has been reported to SourceForge.)