It is also possible that it's creating articles twice, and opening one with the new editor - I just discovered that for each of the 10 articles I made earlier today, I had a blank one of that article template listed as UNTITLED.
Just made 3 dummy articles to confirm - one by pressing the old editor button, one clicking specifically the create button, and one I forget where I clicked - all 3 spawned UNTITLED duplicates. Not sure if this is a related problem or deserves its own bug report.