TYPO3 Core

• have translated records
• export page with all translated content
• do not export the sys_language record, because it got duplicated on import
• all sys_language_uid fields will have a lost relation to the sys_language record

On importing such export all sys_language_uid fields are set to 0
and so all translated records are on default language.

Idea to solve this: on importing there should be a list of records with corresponding uids where from other record fields a lost relation is set to. There you choose to force the old uid (import on the same instance) or to set a alternative one (import on other instance).