Just so you know the following message appears on occasions after a Joomla update 3.6.4
(This happens in the ES 2 RC1 version too)

Cheers!

Error 1062
Duplicate entry '94cd4ff4c99zz9f115e48c13b2127c5f' for key 'session_id' SQL=INSERT INTO `#__social_registrations` (`session_id`,`created`) VALUES ('94cd4ff4c99zz9f115e48c13b2127c5f','2016-10-27 12:49:37')