Inconsistent results from MockService

I have a simple mockservice running on SoapUI 4.5.1 - Windows7.

When I use a mockrequest to call the mockservice, I see this behavior:
- the first request returns the response as expected
- if a second request is immediately executed, a SOAPFault is returned as below
- subsequent requests also return this error
- if I wait for a few minutes and fire again, the behavior resets - the correct response is returned, followed by more errors for subsequent requests

Am seeing this behavior with all my WSDLs... sample is below. Project is attached.

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
   <soapenv:Body>
      <soapenv:Fault>
         <faultcode>Server</faultcode>
         <faultstring>Missing operation for soapAction [] and body element [null] with SOAP Version [SOAP 1.1]</faultstring>
      </soapenv:Fault>
   </soapenv:Body>
</soapenv:Envelope>

WSDL is below:

<?xml version="1.0" encoding="UTF-8"?>
<definitions xmlns="http://schemas.xmlsoap.org/wsdl/" xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:tns="http://www.celcom.com/EMA" targetNamespace="http://www.celcom.com/EMA">
 <types>
  <xs:schema targetNamespace="http://www.celcom.com/EMA">
 <xs:complexType name="EmaProduct">
  <xs:sequence>
   <xs:element name="Id" type="xs:string" minOccurs="0"/>
   <xs:element name="ClassId" type="xs:string" minOccurs="0"/>
   <xs:element name="Speed" type="xs:string" minOccurs="0"/>
   <xs:element name="APN" type="xs:string" minOccurs="0"/>
   <xs:element name="FUP" type="xs:string" minOccurs="0"/>
  </xs:sequence>
 </xs:complexType> 
 <xs:complexType name="ResultStatus">
  <xs:sequence>
   <xs:element name="StatusCode" type="xs:int"/>
   <xs:element name="Message" type="xs:string" minOccurs="0"/>
  </xs:sequence>
 </xs:complexType> 
 <xs:element name="QueryEmaProductRequestMsg">
 <xs:complexType >
  <xs:sequence>
   <xs:element name="EmaProductId" type="xs:string"/>
  </xs:sequence>
 </xs:complexType> 
 </xs:element>
 <xs:element name="QueryEmaProductResultMsg">
 <xs:complexType>
     <xs:sequence>
      <xs:element name="ResultStatus" type="tns:ResultStatus"/>
      <xs:element name="EmaProduct" type="tns:EmaProduct" minOccurs="0"/>
     </xs:sequence>
    </xs:complexType>
 </xs:element>
 <xs:element name="UpsertEmaProductRequestMsg" type="tns:EmaProduct"/>
 <xs:element name="UpsertEmaProductResultMsg">
 <xs:complexType>
     <xs:sequence>
      <xs:element name="ResultStatus" type="tns:ResultStatus"/>
     </xs:sequence>
    </xs:complexType> 
 </xs:element>
   
 </xs:schema>
 </types>
 <message name="UpsertEmaProductRequest">
  <part name="UpsertEmaProductRequest" element="tns:UpsertEmaProductRequestMsg"/>
 </message>
 <message name="UpsertEmaProductResult">
  <part name="UpsertEmaProductResult" element="tns:UpsertEmaProductResultMsg"/>
 </message>
 <message name="QueryEmaProductRequest">
  <part name="QueryEmaProductRequest" element="tns:QueryEmaProductRequestMsg"/>
 </message>
 <message name="QueryEmaProductResult">
  <part name="QueryEmaProductResult" element="tns:QueryEmaProductResultMsg"/>
 </message>
 <portType name="EmaProduct">
  <operation name="UpsertEmaProduct">
   <input message="tns:UpsertEmaProductRequest"/>
   <output message="tns:UpsertEmaProductResult"/>
  </operation>
  <operation name="QueryEmaProduct">
   <input message="tns:QueryEmaProductRequest"/>
   <output message="tns:QueryEmaProductResult"/>
  </operation>
 </portType>
 <binding name="EmaProduct" type="tns:EmaProduct">
  <soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
  <operation name="UpsertEmaProduct">
   <soap:operation soapAction=""/>
   <input>
    <soap:body use="literal"/>
   </input>
   <output>
    <soap:body use="literal"/>
   </output>
  </operation>
  <operation name="QueryEmaProduct">
   <soap:operation soapAction=""/>
   <input>
    <soap:body use="literal"/>
   </input>
   <output>
    <soap:body use="literal"/>
   </output>
  </operation>
 </binding>
 <service name="EmaProduct">
  <port name="EmaProduct" binding="tns:EmaProduct">
   <soap:address location="http://localhost"/>
  </port>
 </service>
</definitions>