[Gelöst] some translated products showing out of stock

Background of the issue:
I have products already translated all fine. I have created some new products and started to translate them using the Printful plugin. These products are all imported from Printful. The issue can be seen here: versteckter Link

Symptoms:
In the Spanish version of the site, the translated products are showing as out of stock, even though I expected them to work correctly.

Questions:
Why are the translated products showing as out of stock?
How can I resolve the out of stock issue for translated products?