When creating a new translation of an entity, translatable filed values are prepopulated with the same values included in the source language.
This is great, but this is not enough in some cases. For instance, if you're creating a new translation for a Field Collection (Cardinality Unlimited) field and you click the "Remove" button before the translation is saved, this leads to some weird behaviors, where disappear all the values but the first.
This bug comes from the
$form_state['field'][$field_name] that it is not updated accordingly to the prepopulated values and contains data related to the empty translation values.
I think that
$form_state['field'][$field_name] values should be also prepupulated to keep consistency and avoid these problems.