Vedran

Problem:
You are experiencing issues with WPML and ACF repeater fields in a multilingual setup using WordPress Classic Editor. Specifically, when you delete a row or change the order of rows in the default language, the translated versions become misaligned. You are looking for a way to prevent repeater row shifting/desync when editing the default language, maintain translation support only for one subfield while keeping other fields copied or fixed, and avoid full manual reordering and re-entry across all languages.
Solution:
This issue is related to a known problem currently under investigation by our developers. You can find more details here: https://wpml.org/errata/advanced-custom-fields-multilingual-reordering-repeater-fields-makes-the-translations-unsynchronised/
When using the WordPress Editor to create translations, ensure all ACF Fields are set to "Copy once". This setting ensures that fields are only copied once and then become editable in the translated content. Additionally, set "ACF Field Groups" at WPML > Settings > Post Type Translation to "Not translatable". More details on setting up ACF fields with WPML can be found here: https://wpml.org/documentation/related-projects/translate-sites-built-with-acf/recommended-custom-fields-translation-preferences-for-acf-and-wpml/

If this solution does not apply to your case, or if it seems outdated, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins. If issues persist, please open a new support ticket at our support forum.