Reported for: Advanced Custom Fields Multilingual 0.3
There is an issue when you have a field created using ACF, with serialized data like “Taxonomies” or “Gallery”, and you set it to copy.
What happens is that the value in the translation is an exact copy of the field in the original post/page (the one in the default language).
This makes the field have no selection or data in the second language. This is because they refer to elements with IDs coming from the other (usually, the original) language.
Until this is resolved, it is recommended to set the fields to Translate and provide the data for these fields manually, in the translations.