Woocommerce Multisite Permalink Problems

I am using Woocommerce on a multisite environment to display two sites in different languages. The root site is English, the subsite is german. Woocommerce is only used as a product catalogue with about thirty products. WP and WC are latest versions.

All links in the root site are working fine, incl. the woocommerce products.

The German site was working fine until some normal work on the product content was done. Now all links to products in the german subsite are broken, every click on a product brings a 404 error, even when triggered from the backend via “view product”.

I tried different permalink structures, searched for similar problems in the web. No success.

I also tried to generate a second subsite from the English root site. That worked in the beginning. But as soon as I changed the permalinks for the german products on this new subsite all products broke. Changing the permalinks back did not help.

I would appriciate all hints, experiences. Please help.

https://ww.wp.xz.cn/plugins/woocommerce/