Getting error while transforming from Cash Sale into Cash Refund in Netuite

Question

I've been making an API request to this netsuite RESTapi endpoints as per this documentation: https://system.netsuite.com/help/helpcenter/en_US/APIs/REST_API_Browser/record/v1/2020.2/index.html#tag-cashSale

I am getting below error on making api call to transform cashsale into cashrefund.

Request Payload :

{
  method: 'post',
  url: 'https://accountID.suitetalk.api.netsuite.com/services/rest/cashSale/cashSale_id/!transform/cashRefund',
  headers: {
    Authorization: 'xxxx',
    'Content-Type': 'application/json',
    Cookie: 'NS_ROUTING_VERSION=LAGGING',
  },
  data: {
    exchangeRate: x,
    entity: {
      id: 'xx',
    },
    location: {
      id: 'xx',
    },
    currency: {
      id: 'xx',
    },
    postingPeriod: {
      id: 'xx',
    },
    customForm: {
      id: 'xx',
      refName: 'xx',
    },
  },
};

Response Error :

{
  detail:
    'Error while accessing a resource. You have entered an invalid default value for this record transformation operation.',
  'o:errorCode': 'USER_ERROR',
};

Is there a way to solve with this error? please assist me.

and for fields reference I am attaching a doc link: https://www.netsuite.com/help/helpcenter/en_US/srbrowser/Browser2017_1/script/record/cashrefund.html

Thanks in advance