In these two edits made with VisualEditor, the infobox was duplicated on save and the duplicate was actually subst'd into the infobox's table:
https://fr.wikipedia.org/w/index.php?diff=94112508
https://fr.wikipedia.org/w/index.php?diff=94163787
The behavior seems to be inconsistent since in the first case, the duplicate was inserted right after the infobox, and in the second case, it was inserted after the first paragraph
Version: unspecified
Severity: major
Another infobox duplicated while the editor is touching something else (not the infobox):
https://ca.wikipedia.org/w/index.php?title=Hurac%C3%A0_de_Cuba_de_1910&diff=11973992&oldid=11973843
Duplication of infoboxes is a big deal, very visible and annoying for editors that have to go and change back. Defining importance just in case this report was unnoticed, although of course this is a call for JamesF. :)
We believe that these cases have now been fixed (though we may be wrong). Please re-open if so.