arnoP-3

Problem:
You are trying to synchronize a 'Post' relationship field automatically when translating content using the Advanced Translation Editor (ATE). You have two Custom Post Types (CPTs): a parent CPT and a child CPT. The child post uses a 'Post' relationship field to select the parent, but when translating from English to German, the field in the German post does not automatically populate with the ID of the corresponding German parent, leaving the relationship field empty.
Solution:
This issue is recognized and will be addressed in a future WPML release (version 4.8). Meanwhile, you can use the

wpml_object_id

hook as a workaround. Set the custom field to 'COPY' so that the translation retains the POST ID (even if it's not the translated one). Use the following PHP code to translate the POST ID in the current language:

// Getting selected post ID:<br />$post_id = rwmb_meta('parent_post');<br />$current_lang = apply_filters('wpml_current_language', NULL);<br />$post_id = apply_filters('wpml_object_id', $post_id, 'parent-post', TRUE, $current_lang);

This code will help display the correct translated post ID on the frontend. Remember, the empty field in the backend is a visual bug and does not affect the actual functionality.

For more details on translating custom fields, visit Translating Custom Fields documentation.

If this solution does not apply to your case, or if it seems outdated, we recommend opening a new support ticket. Also, check related known issues at https://wpml.org/known-issues/, verify the version of the permanent fix, and confirm that you have installed the latest versions of themes and plugins. For further assistance, please contact our support at WPML support forum.