On my site, I have both plain WordPress posts and custom post types, all of them with featured images (which are dynamic). The problem I've run into is that when I change language, even though I have made translatable Media and each one of custom post types, the feature images get corrupted and they don't appear at all. The only way I found how to partially solve it is by editing the page's translated version to recover the image but this is not correct.
Googling hasn't helped much on this very specific bug.
I have investigated the WPML settings and it appears that the system custom field _thumbnail_id (which stores the Featured Image ID) is currently locked to the Do not translate (0) setting. This field does not appear in the Custom Fields Translation list, even when selecting 'Show system fields'. I believe this is preventing the correct synchronization of the image Post ID to the translations. Could you please help me set this field to Copy (1), or confirm the correct method to force this synchronization, as the WPML Media Translation functionality does not seem to be overriding it effectively?
