I have done what you asked and put also 1 post type inside english language. in content i leave a message for you what should happend if i duplicate this post.
Thank you, I was able to reproduce the issue in the testing environment. I've escalated that to our developers and will let you know once I hear from them.
I got feedback from our devs. The issue is that what was being translated was the field value, and not the label. When a value is changed, JetEngine won't keep it's state, as it recognizes that the value is not the same. To have the same result, but to keep the values synchronized across translations, you can follow the steps below:
1. Create the Labels and Values for the checkbox in JetEngine > Glossary (you can have values in lowercase, so it's easier to differentiate them in String Translation, later). Check image attached with example;
2. Inside the JetEngine's Post Type, set the source to Glossary and select the glossary created with the values. Check image;
3. In WPML > Settings > Custom Fields Translations, find the name of the meta field and set it to copy. Check image;
4. Go to WPML > String Translation and make sure that only the Labels are translated. The values should be the same as the original. If you set values in lowercase, it will be easy to differentiate labels and values;
5. Finally, make a small change to the original post that contain the value and update the translation;
That should solve the issue. What was happening, was that we were accidentally translating values. Let me know how it goes.
I got that since the beginning, the instructions I sent are precisely to overcome the fact that "when I click duplicate the value or checkbox isn't checked". The issue is that translated checkboxes get unchecked when translated. To overcome that, please follow the steps I shared. If you wish, here's a video explaining it better: hidden link
We tested and verified this solution. This way the checkboxes value will keep consistent with the original.