SOAP WCF Webservice behaves differently when called locally or remotely

I have a WCF SOAP 1.1 Webservice with the configuration given below.

A co-local call to any method on this endpoint hangs until another returns on a remote call (from another computer on the network).

I cannot replicate this when these methods are called locally (with the client located on the same machine).

I tried to increase maxConcurrentCalls with no luck ... service behavior seems to be different from client local / remote location. Any guess?

Looking at the ServiceModelEndpoint performance counters of the concurrent call script, the results are interesting: remote "calls thrown" reach the limit at 2 calls ... whereas local calls from 20 concurrent threads reach 18 "calls"! Call limit 2 "remote" seems "per process".

Thanks,

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <system.serviceModel>
    <services>
      <service behaviorConfiguration="MyCustomBehavior" name="CONTOSO.CONTOSOServerApi.IContosoServiceApiImplV1">
        <endpoint address="" binding="customBinding" bindingConfiguration="WebBinding"
          bindingNamespace="http://contoso.com" contract="CONTOSO.CONTOSOServerApiInterfaceV1.IContosoServiceApiV1" />
      </service>
    </services>
    <behaviors>
      <serviceBehaviors>
        <behavior name="MyCustomBehavior">
          <serviceMetadata httpGetEnabled="true" httpGetUrl="http://localhost:8080/MyEndPointV1" />
          <serviceDebug httpHelpPageEnabled="false" includeExceptionDetailInFaults="true" />
          <serviceThrottling maxConcurrentSessions="10000" maxConcurrentCalls="1000"/>
          <dataContractSerializer maxItemsInObjectGraph="2147483647" />
        </behavior>
      </serviceBehaviors>
    </behaviors>
    <bindings>
      <customBinding>
        <binding name="WebBinding">
          <textMessageEncoding messageVersion="Soap11" maxReadPoolSize="2147483647" maxWritePoolSize="2147483647">
            <readerQuotas maxDepth="2147483647" maxStringContentLength="2147483647"
            maxArrayLength="2147483647" maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647" />
          </textMessageEncoding>
          <httpsTransport />
        </binding>
      </customBinding>
    </bindings>
  </system.serviceModel>
</configuration>