I have a WooCommerce product page. When I add a new gallery picture to the translation, WordPress doesn't save it. I know how to replace an existing one in different languages but that's not what I want.
After testing in a clean install, I can confirm that this feature do have a different number of images per language in the product gallery does not exist. I have escalated it as a feature request so that our developers can review. I will update here if I receive any information from our team about this implementation.
Our developer found an easy solution (one that I overlooked). There are those two settings:
Duplicate uploaded media to translations
Duplicate featured image to translations
On each product page. We need to uncheck those to prevent the sync of attachments/product gallery and allow to have different images for the translation.
Additionally probably a good idea is to disable the settings in WPML > Settings > Media Translation > How to handle media for new content
This resolved the issue in our test site. Please let me know if it resolves it on your live site as well.