Complete fulfilment orders for different warehouses

I will explain it a bit more with screenshots…

Test with two fulfilment orders
Two warehouse: one for B2C, one for B2B.

The B2B Warehouse has: Big Product as product

The B2C Warehouse has: Small Product as warehouse

When I create an order now, it results in two fulfilment orders: One for B2B Warehouse and one for B2C Warehouse:

So far: All Good.

Now I send an API request as below:
url: /admin/api/2021-07/orders/4112281206983/fulfillments.json
POST

{ fulfillment: 
   { tracking_company: 'DHL Express',
     location_id: 65337262279,
     tracking_number: '3SHOPK602172701',
     tracking_urls: [ 'https://www.dhlparcel.nl/nl/consument/volg-je-pakket?tc=3SHOPK602172701&pc=9999AA' ],
     notify_customer: true } }

The result is:
{“errors”:{“base”:[“None of the items are stocked at the new location.”]}}

Test with one fulfilment order:

Another test with a new order with only one item. This results in a successful POST request:

This was now set up in a completely new development store. Keep getting stuck. To my humble opinion this is a bug in Shopify.

Regards, Peter