MDSCHEMA_MEMBERS doesn't return members when passing MEMBER_NAME constraint with TREE_OP = 1

Question

When I try to return the child members using the MDSCHEMA_MEMBERS rowset call It keeps failing when the MEMBER_NAME value is passed as part of the request. The below request succeeds:

<CUBE_NAME>Adventure Works</CUBE_NAME>
<DIMENSION_UNIQUE_NAME>[Customer]</DIMENSION_UNIQUE_NAME>
<HIERARCHY_UNIQUE_NAME>[Customer].[City]</HIERARCHY_UNIQUE_NAME>
<LEVEL_UNIQUE_NAME>[Customer].[City].[(All)]</LEVEL_UNIQUE_NAME>
<LEVEL_NUMBER>0</LEVEL_NUMBER>
<MEMBER_UNIQUE_NAME>[Customer].[City].[All Customers]</MEMBER_UNIQUE_NAME>
<TREE_OP>1</TREE_OP>

while the following request fails:

<CUBE_NAME>Adventure Works</CUBE_NAME>
<DIMENSION_UNIQUE_NAME>[Customer]</DIMENSION_UNIQUE_NAME>
<HIERARCHY_UNIQUE_NAME>[Customer].[City]</HIERARCHY_UNIQUE_NAME>
<LEVEL_UNIQUE_NAME>[Customer].[City].[(All)]</LEVEL_UNIQUE_NAME>
<LEVEL_NUMBER>0</LEVEL_NUMBER>
<MEMBER_NAME>All Customers</MEMBER_NAME>
<MEMBER_UNIQUE_NAME>[Customer].[City].[All Customers]</MEMBER_UNIQUE_NAME>
<TREE_OP>1</TREE_OP>

The problem is I'm using MSADOMD objects to access the metadata definitions and it is generating the above request that is failing. I'm not sure if this is an issue with the driver/server or if I can somehow alter my requests to work around this issue.