@ChrisFernandez and @congalong: Mattermost 3.8.2 is available for download here: http://about.mattermost.com/download/
The dot release should fix the WebSocket connection issues you've described.
Please let us know if you hit any further issues, and thank you for the report!
PS: @congalong You may have grabbed an invalid build for 3.8.2: the first release build automation didn't finish successfully, so we re-launched it afterwards. Can you try again, taking the build from http://about.mattermost.com/download/?