XF 1.4 Server error: duplicate entry '105609-113353' for key 'PRIMARY'

[imthebest]

I got the following error logged:

Server Error Log
Error Info
Zend_Db_Statement_Mysqli_Exception: Mysqli statement execute error : Duplicate entry '105609-113353' for key 'PRIMARY' - library/Zend/Db/Statement/Mysqli.php:214
Generated By: user123, 46 minutes ago
Stack Trace

#0 /my_path/library/Zend/Db/Statement.php(297): Zend_Db_Statement_Mysqli->_execute(Array)
#1 /my_path/library/Zend/Db/Adapter/Abstract.php(479): Zend_Db_Statement->execute(Array)
#2 /my_path/library/Zend/Db/Adapter/Abstract.php(574): Zend_Db_Adapter_Abstract->query('INSERT INTO `xf...', Array)
#3 /my_path/library/XenForo/DataWriter.php(1624): Zend_Db_Adapter_Abstract->insert('xf_user_follow', Array)
#4 /my_path/library/XenForo/DataWriter.php(1613): XenForo_DataWriter->_insert()
#5 /my_path/library/XenForo/DataWriter.php(1405): XenForo_DataWriter->_save()
#6 /my_path/library/XenForo/Model/User.php(1765): XenForo_DataWriter->save()
#7 /my_path/library/XenForo/ControllerPublic/Member.php(473): XenForo_Model_User->follow(Array)
#8 /my_path/library/XenForo/FrontController.php(347): XenForo_ControllerPublic_Member->actionFollow()
#9 /my_path/library/XenForo/FrontController.php(134): XenForo_FrontController->dispatch(Object(XenForo_RouteMatch))
#10 /my_path/index.php(13): XenForo_FrontController->run()
#11 {main}

Request State

array(3) {
  ["url"] => string(133) "http://www.mysite.com/members/someone.456/follow?_xfToken=105609%2C1412778890%2Cdb29f78f8b8c6bb013ab99f9b0db6a0b91fb4de2"
  ["_GET"] => array(1) {
    ["_xfToken"] => string(58) "105609,1412778890,db29f78f8b8c6bb013ab99f9b0db6a0b91fb4de2"
  }
  ["_POST"] => array(5) {
    ["_xfConfirm"] => string(1) "1"
    ["_xfRequestUri"] => string(28) "/members/someone.456/"
    ["_xfNoRedirect"] => string(1) "1"
    ["_xfToken"] => string(8) "********"
    ["_xfResponseType"] => string(4) "json"
  }
}

Is this bad? Duplicate primary key? Is this data corruption?

It is a forum migrated from vBulletin 3.8.5. It has been (and it is) working fine for about 2 months now.

 

[Mike]

It can be disregarded.

 

[imthebest]

Is this a bug? Or just a random thing that might happen randomly?

 

[Mike]

It's a race condition. It can happen infrequently.