Cant delete mappings of 1:n connection

Question

Hi all, 
is this normal, or is there an error on our crm server?
I have a 1:n connection from contact to an custom entity.
if i go to mappings of this connection i see that by standard all other 1:n connections (only from contact to the same custom entity) have an mapping entry like this:
sourcename   / destinationname
contactid ... Contact / new_example1id ... Example 1
contactid ... Contact / new_example2id ... Example 2
I only wanted to map 1 of these lookups, not all, because the problem ist .. that if i create a new custom entity entry from out of my contact, all these contact-fileds will be filled automatically with the contact entry, from which i started the creation
of the new custom entity entry. But this is wrong.
Can anyone test this, if this is wrong by design?
MANY MANY THX to all..
Greetings, Pit

Answer 1

If i want to delete the other not necessary mappings, i geht the following error and cant delete it .. and this is the problem. I need to delete this?
I want to know if this is planed from ms, to can not delete this, or if this is an issue with our config / server?!
Cannot create or delete a system AttributeMap.
Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=5.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: System.Web.HttpUnhandledException:
Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #C74E3128Detail: 
<OrganizationServiceFault xmlns:i="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://schemas.microsoft.com/xrm/2011/Contracts">
  <ErrorCode>-2147220970</ErrorCode>
  <ErrorDetails xmlns:d2p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
  <Message>System.Web.HttpUnhandledException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #C74E3128</Message>
  <Timestamp>2013-03-04T11:08:58.0272169Z</Timestamp>
  <InnerFault>
    <ErrorCode>-2147196411</ErrorCode>
    <ErrorDetails xmlns:d3p1="http://schemas.datacontract.org/2004/07/System.Collections.Generic" />
    <Message>Cannot create or delete a system AttributeMap.</Message>
    <Timestamp>2013-03-04T11:08:58.0272169Z</Timestamp>
    <InnerFault i:nil="true" />
    <TraceText i:nil="true" />
  </InnerFault>
  <TraceText i:nil="true" />
</OrganizationServiceFault>