This thread is resolved. Here is a description of the problem and solution.
Problem: My website is in English (main) and French. I have several CPT and several ACF (including repeater field) foreach CPT. I use Multilingual Content Setup to choose how to translate each field.
When I try to edit an option into the MCS Post metabox, click on Apply, my current Post is duplicated several times and is directly published. It's even doing that just clicking on Apply actually.
Solution: To solve my problem, I had to fill the "Translation preferences" option for each ACF field, an option which didn't exists when I built the site.
This is the technical support forum for WPML - the multilingual WordPress plugin.
Everyone can read, but only WPML clients can post here. WPML team is replying on the forum 6 days per week, 22 hours per day.