When i alter a form via hook_form_alter and add some elements to #option they will be shown in the array with dsm($form) at the right place and other select widgets do it right. the reason i could find could be that the html with the option elements is prebuild and saved in the #prefix element so it cant be edited via form_alter functions.
Comments
Comment #1
giorgosksimilar issue that comes from the same implementation incompatibility I believe
entity translation lately adds (all languages) to the label of all fields that are shared between all languages for usability purposes (using the function entity_translation_element_translatability_clue)
a field with multiselect widget for a shared field will have the field title untouched even though the element passes by the function entity_translation_element_translatability_clue
Comment #2
mparker17multiselect-7.x-1.9 is no longer supported, because Drupal 7 is no longer supported.
Can you confirm if this is still an issue in multiselect-2.0.0-beta4?
I'm going to mark this issue as "Postponed (maintainer needs more info)"... but when you answer, please change it back to "Active". If there is no reply in ~6 months, then I will mark this issue as "Closed (outdated)". Thank you in advance for your understanding and patience as I try to keep this module's issue queue clear.