Opening client xsd in visual studio crashing visual studio?

I am trying to open xsd in visual studio and its crashing viual studio.

I tried to open xsd in xml editor and able not able to figure out exactly .. but seems like some issue with Grup and sequence

<xs:importnamespace="http://XYZ"schemaLocation="XYZ.xsd"/>

  <xs:redefineschemaLocation="../ABC/123.xsd">

   <xs:groupname="Ptest">

     <xs:sequence>

       <xs:groupref="Ptest"/>

       <xs:groupref="Contents"/>

     </xs:sequence>

   </xs:group>

   <xs:groupname="Test2">

     <xs:sequence>

       <xs:group ref="Test2"/>

       <xs:groupref="SContents"/>

     </xs:sequence>

   </xs:group>

  </xs:redefine>

  <xs:groupname="Contents">

   <xs:sequence>

     <xs:elementref="sdm:Field1"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Field2"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Field3"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Field4"minOccurs="0"maxOccurs="1"/>

     <xs:elementref="sdm:Field5"minOccurs="0"maxOccurs="1"/>

   </xs:sequence>

  </xs:group>

  <xs:groupname="SContents">

   <xs:sequence>

     <xs:elementref="sdm:FieldRef"minOccurs="0"maxOccurs="unbounded"/>

   </xs:sequence>

  </xs:group>

It looks like looping can any one let me know the cuase of crashing visual studio