Important: #110653 - Unidirectional MM relations are copied during localization 

See forge#110653

Description 

When a translatable record with a unidirectional many-to-many relation is localized, the relation is now copied to the translated record.

Previously, every MM field without MM_opposite_field was considered the local side of a bidirectional relation. This also matched unidirectional MM fields and caused their relations to be omitted during localization.

TYPO3 now omits relations only when the field declares MM_oppositeUsage or another field points back to it through MM_opposite_field .

Affected installations 

Installations with translatable records that use unidirectional MM fields are affected.

Migration 

No configuration change is required. Relations already omitted from existing translations must be restored manually.