Getting property invalid error! /IWCOR/CX_DS_EP_PROPERTY_ERROR!

Hi experts,

   My data model and association is as below

  I have implemented CREATE_DEEP_ENTITY method.

But when I run the service in gateway client I get error:

<code>/IWCOR/CX_DS_EP_PROPERTY_ERROR/xxxxx</code>

<message xml:lang="en">Property 'ITEM_DATA' is invalid</message>

I have given my json input as below:

{

       "DELIVERY_NUMBER": "",

       "SHIP_TO_TYPE": "O",

       "ORIGINATOR": "ABCD",

"ITEM_DATA": [{

       "DELIVERY_NUMBER": "",

       "ITEM_NUMBER": "1",

       "QUANTITY": "12",    

       "PLANT": ""

    }]

}

What is wrong here? Why am I getting this error?  Please help!

Thanks

Gopal