Multilingual and Mailings: the interface only displays the groups selected in a given language

This is a weird bug:

• Enable multi-lingual, and enable a second language (ex: English & French)
• Create a new mailing while in English
• Add a group to the list of recipients.
• Save the draft

Now switch the interface language to the other language (ex: French), and edit the mailing. Notice that the group has disappeared. It's not gone, but hidden.

In my case, the mailing was re-used from EN to FR, and since the groups were not visible, and there are different mailing groups for each language, the mailing ended up being sent to both language recipients.