But it does not work, because the association with authors will return empty authors for the Material as the materials are also soft deleted.

The problem is that Globalize knows nothing about acts_as_paranoid. You can delete a Material, and it should delete the translations, but when you try to recover the Material then there is an error because of how the translations are implemented and the order in which the translations and the Material are recovered. Which record should be recovered first?

Remember that the Material has all of its translations for the title in a table that just got soft deleted. So the correct answer is “nil”. The title of the delete material is nil.