Check out the issue raised by Payless regarding TL's for Inter Island that were scanned but with zero quantity upon submission to ewms portal.
Steps. 
a. Check wms_letdown_list to check the ist of letdown document
b. Check wms_letdown_details and upon checking there were SKU's with zero scan quantity
c. Update wms_letdown_details and revert back the quantity of the SKU's under the affected letdown document back to zero
d. Instructed Payless warehouse to re-assign again the letdown
