Schemavalidate gives lsx-00023 intermittently, reporting garbage namespace

Question

I am getting the error "LSX-00023: unknown namespace URI" intermittently from xmltype.schemavalidate. The URI shown in the error message is a series of garbage characters, usually starting with 4 'y's with umlauts (must be a name for that, but I don't know it), then a series of other characters mostly not generally found on my keyboard, other accented characters, squares, etc. The error may or may not happen on identical XML, I can sit with PL/SQL Developer hitting execute on the same script and it usually shows the error the first time, then may work fine for 4, 6, 8 executions before failing again. The XML is valid, I can validate it with other tools, here's a sample:
<?xml version="1.0" standalone="yes"?>
<metadata version="1.0" xmlns="http://schemas.syp.police.uk/actionMetadata" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
<plan xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="bailPlanType" taskType="BRREQ">
<custodySerialNumber>652897</custodySerialNumber>
<custodyReference>
<bcu>H</bcu>
<number>1332</number>
<year>2009</year>
</custodyReference>
<bailedPerson>
<bailedPersonSerialNumber>NOM-1234567</bailedPersonSerialNumber>
<name>
<surname>XXXX</surname>
<firstName>YYYY</firstName>
<middleName>ZZZZ</middleName>
</name>
<dateOfBirth>1985-03-21</dateOfBirth>
<pncNumber xsi:nil="true" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/>
</bailedPerson>
</plan>
<action xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="bailReleaseRequestActionType" taskType="BRREQ">
<bail>
<id>522687</id>
<officerInCase>
<ns3:officerSerialNumber xmlns:ns3="http://schemas.syp.police.uk/common">39211</ns3:officerSerialNumber>
<ns3:name xmlns:ns3="http://schemas.syp.police.uk/common">
<ns3:surname>AAAA</ns3:surname>
<ns3:firstName>BBBB</ns3:firstName>
<ns3:middleName/>
</ns3:name>
<ns3:sex xmlns:ns3="http://schemas.syp.police.uk/common">MALE</ns3:sex>
<ns3:rank xmlns:ns3="http://schemas.syp.police.uk/common">DS</ns3:rank>
<ns3:collarNumber xmlns:ns3="http://schemas.syp.police.uk/common">956</ns3:collarNumber>
<ns3:employeeReferenceNumber xmlns:ns3="http://schemas.syp.police.uk/common">006301</ns3:employeeReferenceNumber>
<ns3:unit xmlns:ns3="http://schemas.syp.police.uk/common">A</ns3:unit>
</officerInCase>
<bailedTo>
<code>H1</code>
<description>ABCDEFG</description>
</bailedTo>
<dateTimeSurrender>2009-04-01T09:00:00</dateTimeSurrender>
</bail>
<releaseRequest>
<requester>
<id>3400055</id>
<name>AAA, BBBB, CCCC</name>
</requester>
<responder>
<id>35927</id>
<name>TEST-CASELOAD</name>
</responder>
<reason>qqq</reason>
<evidenceOfAuthority>aaa</evidenceOfAuthority>
</releaseRequest>
</action>
</metadata>
Any ideas on how to proceed would be appreciated. I also notice that when I write out the xml with dbms_output.put_line, it always stops part way through the xml (after the <description> element), not sure if that might be related.

Answer 1

I have now submitted this to Oracle as a service request.
It seems to be somehow related to the client, though I don't see how since the code is executing on the server, and all the data is there, the client is just calling a package procedure, passing a number. The error only seems to happen when using a windows client, whether SQLPlus, PL/SQL developer or JDBC (Oracle Thin driver). I've tried several XP machines, both 32 & 64 bit, both of which show the problem. When running the same thing on sqlplus running on the database host (which is running Solaris), or via JDBC from an application server (running Red Hat), I don't see the error.