Running the 14 Nov 2017 master build on igniterealtime's Openfire. A simple reproducer.
Log in with our groupchat
Observe admin console shows valid session with green status
Close web browser tab (Chrome for me at least)
Observe admin console showing session as closed, but still listed.
Attempt to close the session via the admin console, a green success appears, but session still listed.
Good news (I suppose), I was easily able to reproduce this on my development laptop.
I figured this was (session resumption) related and it appears to be. This does not reproduce on a build from the day prior to this code going into master.