TYPO3 Core

If a records has a child records as IRRE relation with foreign field,
but the child records also exist freely without parent record and the
default value for the foreign field is 0 (Zero), then translating
the parent records will delete all child records without a parent.

Bonus: If the child records is not translatable, a "translated" child
record is created anyway.

Expected behavior:
Translated parent and do not show child record IRRE in the translation
(Formengine).
Free children are left alone.
Bonus: Do not create a new child record for each translation.

Actual behavior:
Child record relation is not shown in translation (form engine). [correct]
All free children are removed. [big problem]
Bonus: A new child record is created for each translation. [small problem]

Workaround:
Make the default value for the foreign field not zero (e.g. -1).