data.shipments[0].pickup.retail_network_id NULL value found, but a string is req

This error appears when trying to export a label/shipment to PostNL which has a Pick-up location selected.

data.shipments[0].pickup.retail_network_id NULL value found, but a string is required (Code 0)

Then also, the “Afhalen bij PostNL” is not showing the location in the admin’s order details page:

Afhalen bij PostNL:
, ,