This thread is resolved. Here is a description of the problem and solution.
Problem: When switching languages between WooCommerce product categories, the user gets a 404 error.
Solution: Translating the slug and deactivating a conflicting plugin solved the problem.
1. Go to WPML > Theme and plugins localization and select Translate by WPML 2. Scroll down to "Strings in the plugins" and select WooCommerce and scroll down to click the blue button "Scan the selected plugins for strings" 3. WPML > String translation and search for "product-category" and translated Url product_cat slug: product-category to product-categorie. This solves going from en to nl, but to go from en to nl, I needed to deactivate the plugin WooCommerce NL.
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