Using of special names in custom taxonomies may break the language switcher

Overview of the issue

1. Create a custom taxonomy called “taxonomy”.
2. Create a template for that taxonomy.
3. Add some terms to that taxonomy.
4. Add a post with one of those three terms attached to it.
5. Translate the post and the three terms to another language.
6. Visit the archive of that taxonomy.

Workaround

Don’t use “taxonomy” as custom taxonomy name.
When creating a custom taxonomy which is called, for instance, “taxonomy”, the language switcher stops working when used in a custom theme archive template.