Alright, found the problem. Seems that with the new Jessie foundation, supervisord no longer sets the $HOME variable. Here’s what you’ll do to fix it and I’ll hopefully get this fix onto the new ISO soon before more of this issue arises:
echo 'environment=HOME="/root",USER="root"' >> /etc/supervisor/conf.d/mineos.conf
supervisorctl reread
supervisorctl update
Log back into the webui and it should work now.
UPDATE: this is fixed in the current Jessie ISO now.