SSL Breaks Message Inspector (WCF bug?)

Question

I have a custom message inspector that executes this line of code:

 public object AfterReceiveRequest(ref Message request, IClientChannel channel, InstanceContext instanceContext)
 {
     MessageBuffer contextPatch = request.CreateBufferedCopy(1024 * 128);
     ...
 }

The CreateBufferedCopy works fine when no security is enabled, but it throws an InvalidOperationException when SSL is configured. The exception claims that the Message request object is in the "Written" state. The configuration for all this is here:

  <serviceBehaviors>
    <behavior>
      <serviceCredentials>
        <clientCertificate>
          <authentication certificateValidationMode="PeerTrust" />
          <certificate findValue="sigtest.arbit.com" storeLocation="LocalMachine" storeName="My" x509FindType="FindBySubjectName" />
        </clientCertificate>
        <serviceCertificate findValue="sigtest.arbit.com" storeLocation="LocalMachine" storeName="My" x509FindType="FindBySubjectName" />
      </serviceCredentials>
      <serviceDebug includeExceptionDetailInFaults="false" />
      <serviceMetadata httpGetEnabled="false" httpsGetEnabled="true" />
      <serviceSecurityAudit auditLogLocation="Application" messageAuthenticationAuditLevel="Failure" serviceAuthorizationAuditLevel="Failure" suppressAuditFailure="true" />
      <endToEndLogging traceKeys="CorrelationId|correlationId" createDefaultRequestValue="false" />
    </behavior>
  </serviceBehaviors>

This seems to be a bug in WCF itself. That is, the Message request parameter should not be left (by SSL functionality?) in the "written" state. Thoughts?

In case it is relevant, a custom binding was used for SSL:

  <customBinding>
    <binding name="myCustomBinding">
      <security defaultAlgorithmSuite="Default" authenticationMode="MutualCertificateDuplex" enableUnsecuredResponse="true" requireDerivedKeys="false" securityHeaderLayout="Lax" includeTimestamp="true" messageProtectionOrder="EncryptBeforeSign" messageSecurityVersion="WSSecurity11WSTrustFebruary2005WSSecureConversationFebruary2005WSSecurityPolicy11BasicSecurityProfile10" requireSignatureConfirmation="false" allowSerializedSigningTokenOnReply="true">
        <localClientSettings detectReplays="true" />
        <localServiceSettings detectReplays="true" />
      </security>
      <textMessageEncoding messageVersion="Soap11" />
      <transactionFlow />
      <httpsTransport />
    </binding>
  </customBinding>