Hipchat Data Center: Cannot disconnect my stale chat sessions

Summary

When I go to https://<fqdn>/account/sessions and try to disconnect an old session by hitting Disconnect, the session doesn't go away.

Environment

Hipchat Data Center 3.1.1 and earlier

Steps to Reproduce

We don't know the root cause of this issue yet so we can't reproduce it

Expected Results

The session should go away

Actual Results

The session is reported in the UI as have been disconnected but is still visible, the following will appear in /var/log/hipchat/web.log:

2017-11-01T09:48:14.859569+00:00 hn1 web[2014]: account/sessions#REQADB67B uid-1 48ms [info] Disconnecting session 1:web||proxy|192.168.200.235|5242 on proxy:192.168.200.235:5242 with condition=conflict and text=Disconnected via web interface.
2017-11-01T09:48:14.865254+00:00 hn1 web[2014]: account/sessions#REQADB67B uid-1 53ms [error] Tetra API error: Session 1:web||proxy|192.168.200.235|5242 not connected here

Workaround

The session keys should be deleted from Redis. Contact Hipchat Server Support for the workaround steps.