Fehler nach Update - PHP Fatal error: Cannot redeclare class Zend_Db_Select

Folgenden Fehler erhalten wir aktuell in unserer php_errors.log: 

Stack trace:
#0 /html/shopware/engine/Library/Zend/Db/Statement/Pdo.php(228): PDOStatement->execute(Array)
#1 /html/shopware/engine/Library/Zend/Db/Statement.php(303): Zend_Db_Statement_Pdo->_execute(Array)
#2 /html/shopware/engine/Library/Zend/Db/Adapter/Abstract.php(480): Zend_Db_Statement->execute(Array)
#3 /html/shopware/engine/Library/Zend/Db/Adapter/Pdo/Abstract.php(238): Zend_Db_Adapter_Abstract->query('INSERT INTO `s_...', Array)
#4 /html/shopware/engine/Library/Enlight/Components/Db/Adapter/Pdo/Mysql.php(96): Zend_Db_Adapter_Pdo_Abstract->query('INSERT INTO `s_...', Array)
#5 /html/shopware/engine/Library/Zend/Db/Adapter/Abstract.php(576): Enlight_Components_Db_Adapter_Pdo_Mysql->query('INSERT INTO `s_...', Array)
#6 /html/shopware/engine in /html/shopware/engine/Library/Zend/Db/Statement/Pdo.php on line 234
[15-Aug-2016 08:42:56 Europe/Berlin] PHP Fatal error: Cannot redeclare class Zend_Db_Select in /home/www/p123456/html/shopware/engine/Library/Zend/Db/Select.php on line 44
[15-Aug-2016 08:42:58 Europe/Berlin] PHP Fatal error: Cannot redeclare class Zend_Db_Select in /home/www/p123456/html/shopware/engine/Library/Zend/Db/Select.php on line 44
[15-Aug-2016 08:43:11 Europe/Berlin] PHP Fatal error: Cannot redeclare class Zend_Db_Select in /home/www/p123456/html/shopware/engine/Library/Zend/Db/Select.php on line 44
[15-Aug-2016 09:07:20 Europe/Berlin] PHP Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry 'ad9e2b39e8d078839f91fcbfa69af496c02f3fc3cbabb4a853b93ce2094f2bd7' for key 'PRIMARY'' in /html/shopware/engine/Library/Zend/Db/Statement/Pdo.php:228

Kann damit jemand was anfangen? Der Fehler wiederholt sich alle ~30 Minuten und immer steht ein anderer “Duplicate Entry” Key drin…