PrestaShop – wrong category breadcrumbs
In case you are suffering with the category page breadcrumbs, which look like nonsence, showing totally unrelated categories, solution may be quite simple (eventhough unacceptable). There may be wrong categories in table ps_category, which have parent category id linking to non existing category. In the moment you delete all rows with not-existing parent-ids, the breadcrumbs will be fixed.
This happen in the case you created some categories and deleted them, but the deletion mechanism in Prestashop is buggy.