Error while adding a custom field value using CustomFieldList class

Hi,

I have generated client side code using wsdl1.3.1 in java.
When I try adding a custom field value to a customer record I get the following error:An unexpected error occurred.

The custom field value is a list type value and here is my code:
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ListOrRecordRef lorr = new ListOrRecordRef();
lorr.setInternalId("5"); //Live Merchant

CustomFieldList customFieldList = new CustomFieldList();
  SelectCustomFieldRef selectCustomFieldRef[] = new SelectCustomFieldRef[1];
  selectCustomFieldRef[0] = new SelectCustomFieldRef();
  selectCustomFieldRef[0].setInternalId("custentity_custtype");
  selectCustomFieldRef[0].setValue(lorr);
  customFieldList.setCustomField(selectCustomFieldRef);
  customer.setCustomFieldList(customFieldList);
 
  WriteResponse response = port.add(customer);
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Q. May I know what is the problem with my code?

Thanks you!