Background of the issue:
I am trying to copy products from one WooCommerce-based online store to another. The store is translated from Polish into English, German, French, Italian, and Spanish using WPML. I used the default WooCommerce import/export function and the WPML import/export extension. Link to a page where the issue can be seen: hidden link
Symptoms:
The products and attributes import correctly, but the categories have random language assignments. In the WooCommerce > Products view, they seem correct, but in the category view or the WooCommerce Multilingual category view, there is chaos.
Questions:
What could be the cause of the random language assignments for categories?
How can we fix the issue with category language assignments?
If it does not work or there are too many. You may try creating a product that includes all the categories and translate it. Import just that product and check everything works fine and then import the rest of the products.