"Purchase Order Line has not been created" error appears, though PO lines were created

This error message appeared persistently when trying to create a PO line item. Nevertheless the PO line items were indeed created.

I do not know under what circumstances the bug might be reproduced, but the following were the fields of the PO line:

POL number - 10090-1
Acquisition method - Gift
Order format - Physical resource
List unit price - 32
Quantity physical - 1
Vendor ref number - 234
Vendor ref type - Internal vendor number
Material supplier - Missing Link Versandbuchhandlung eG
Create inventory - Instance, Holding
Location Name (Code) - Rara-samlingen (HRAR)
Location Quantity Physical - 1