If "Disable translation" is enabled on the attribute this function take care of cloning the attribute from the main language. Since it's missing, changes in the main translation is not propagated to the other translations.

Steps to reproduce

• Set the attribute as not translatable ("Disable translation")
• Create a object
• Translate it to another language
• Edit the first language and change something( VAT or VAT ex./ inc )
• Check that the attribute data in the databse, the translations are not in sync (data_text)