duplicate session key

[liowalter]

In sb-uvf21 log

@edelm : any clue ?

[Mon Jan 20 14:07:34.810774 2020] [php7:error] [pid 21149] [client 131.152.228.242:51845] PHP Fatal error:  Uncaught Zend\\Db\\Adapter\\Exception\\RuntimeException: Duplicate entry 'k0t5dqde7vh8a3j91pkh1k0346' for key 'session_id' in /usr/local/vufind/httpd/vendor/zendframework/zend-db/src/Adapter/Driver/Mysqli/Statement.php:262
Stack trace:
#0 /usr/local/vufind/httpd/vendor/zendframework/zend-db/src/RowGateway/AbstractRowGateway.php(165): Zend\\Db\\Adapter\\Driver\\Mysqli\\Statement->execute()
#1 /usr/local/vufind/httpd/module/VuFind/src/VuFind/Db/Table/Session.php(106): Zend\\Db\\RowGateway\\AbstractRowGateway->save()
#2 /usr/local/vufind/httpd/module/VuFind/src/VuFind/Session/Database.php(56): VuFind\\Db\\Table\\Session->readSession('k0t5dqde7vh8a3j...', '3600')
#3 [internal function]: VuFind\\Session\\Database->read('k0t5dqde7vh8a3j...')
#4 /usr/local/vufind/httpd/vendor/zendframework/zend-session/src/SessionManager.php(140): session_start()
#5 /usr/local/vufind/httpd/module/VuFind/src/VuFind/Session/ManagerFactory.php(154): Zend\\Session\\SessionManager->start()
#6 /usr/local/vufind/httpd/vendor/zendframework/zend-servicemanager in /usr/local/vufind/httpd/vendor/zendframework/zend-servicemanager/src/ServiceManager.php on line 771, referer: https://www.swissbib.ch/Record/278154212