I am the Czech lang maintainer. I believe this is what happened: after the step 2, those 8 strings for the French were kept in your stage. The step 3 added some more strings in Czech. So the stage contained both French strings and the Czech strings in the step 4. AMOS in this case splits all staged strings into chunks per language and submits them all individually for contribution (using the same subject message for all of them).
So Nicolas received those 8 strings submitted again and I got those Czech ones.
Assignee column is empty until the maintainer explicitly assigns the contribution to themselves (clicking at "Start review" or "Assign to me" buttons). That is intentional feature. AMOS automatically informs maintainers about new contributions but it does not assign them.
If you run into the same situation again, you may want to
- either clear your stage before working on another language
- or prepare the translation for all languages and submit them at once - AMOS would split the stage into chunks per language and dispatch them for inclusion