As mentioned, I have found a workaround by manually updating the translated content (by clicking on the Update button).
Unfortunately, this is not an acceptable solution ; the RFG on the translated item should be displayed without having to switch to the the translated item and updating it by hand.
Then I checked the "Debug information" you provided:
There isn't the Toolset or WPML plugins in it.
I suggest you try these:
1) Upgrade your Toolset or WPML plugins to the latest version, you can download Toolset plugins here: https://toolset.com/account/downloads/
2) In case it is a compatibility problem, please deactivate all other plugins, and switch to wordpress default theme 2020, deactivate all custom PHP/JS code snippets, and test again
4) If the problem still persists, please provide database dump file(ZIP file) of your website, also point out the problem page URL and view URL, I need to test and debug it in my localhost, thanks https://toolset.com/faq/provide-supporters-copy-site/
I can install your database dump file in my localhost with a fresh WordPress installation + the latest version of Toolset plugins + WPML plugins, and checked the URLs you mentioned above, I can see the RFG displayed under "Project details", see screenshot: eng.JPG
Please provide detail steps to duplicate the same problem.
I have reproduced the WPML bug, that is :
1. Creating a content in english language with a RFG (versteckter Link)
2. Translating this content to french language. Though the RFG fields are populated, they don't display on the front-end (versteckter Link). My workaround to have it working is to switch to the french translation with WordPress post editot and saving it, which is not an acceptable solution.
Thans for the details, I have checked it in your database file, the problem is in view "Projet single - Points clés"( ID: 58103)
in section "Ordering", you are using below option: order by custom field "Field - toolset-post-sortorder", since those repeatiable field group items do not have a custom field when you translate the post with WPML classic editor, so it conducts the problem you mentioned above.
I have escalated this issue, will update here if there is any news. Currently, you will need to translate the post with WP post editor.