Unable to Import data in "Documents to apply" tab in "Payments and Application" Screen

I created an import to load data into the Payments and Applications screen, Documents to Apply tab. When running the import, it fails with the error: “Value cannot be null. Parameter name: row.” Please advise on the cause and required fix.

My Settings:

using PX.Data;
using PX.Objects.AR;
using ARAdjust = PX.Objects.AR.ARAdjust;
using ARPayment = PX.Objects.AR.ARPayment;

namespace import1.GraphExt
{
    public class ARPaymentEntryExt : PXGraphExtension<ARPaymentEntry>
    {
        [PXImport(typeof(ARPayment))]
        public PXSelect<
            ARAdjust,
            Where<
                ARAdjust.adjgDocType, Equal<Current<ARPayment.docType>>,
                And<ARAdjust.adjgRefNbr, Equal<Current<ARPayment.refNbr>>>>,
            OrderBy<Asc<ARAdjust.released, Asc<ARAdjust.adjdRefNbr>>>> Adjustments;
     }

}