Fehler an Shopbetreiber senden: Error per E-Mail

Hallo zusammen!

Mein Kunde bekommt folgende Fehlermeldung per E-Mail zugesendet, wenn er im BAckend einstellt, dass Fehler an den Shopbetreiber gesendet werden sollen.

ERROR
Message:	exception 'Zend_Session_Exception' with message 'Zend_Session::start() - /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Zend/Cache/Backend/File.php(Line:949): Error #2 mkdir(): File exists' in /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Zend/Session.php:504
Stack trace:
#0 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Plugins/Default/Backend/Auth/Bootstrap.php(385): Zend_Session::start(Array)
#1 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Event/Handler/Plugin.php(149): Shopware_Plugins_Backend_Auth_Bootstrap->onInitResourceBackendSession(Object(Enlight_Event_EventArgs))
#2 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Event/EventManager.php(251): Enlight_Event_Handler_Plugin->execute(Object(Enlight_Event_EventArgs))
#3 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Components/DependencyInjection/Container.php(174): Enlight_Event_EventManager->notifyUntil('Enlight_Bootstr...', Array)
#4 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Components/DependencyInjection/Container.php(157): Shopware\Components\DependencyInjection\Container->doLoad('backendsession')
#5 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Plugins/Default/Backend/Auth/Bootstrap.php(399): Shopware\Components\DependencyInjection\Container->load('BackendSession')
#6 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Event/Handler/Plugin.php(149): Shopware_Plugins_Backend_Auth_Bootstrap->onInitResourceAuth(Object(Enlight_Event_EventArgs))
#7 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Event/EventManager.php(251): Enlight_Event_Handler_Plugin->execute(Object(Enlight_Event_EventArgs))
#8 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Components/DependencyInjection/Container.php(174): Enlight_Event_EventManager->notifyUntil('Enlight_Bootstr...', Array)
#9 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Components/DependencyInjection/Container.php(138): Shopware\Components\DependencyInjection\Container->doLoad('auth', 1)
#10 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Plugins/Default/Backend/Auth/Bootstrap.php(219): Shopware\Components\DependencyInjection\Container->get('Auth')
#11 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Plugins/Default/Backend/Auth/Bootstrap.php(200): Shopware_Plugins_Backend_Auth_Bootstrap->checkAuth()
#12 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Event/Handler/Plugin.php(149): Shopware_Plugins_Backend_Auth_Bootstrap->onPreDispatchBackend(Object(Enlight_Controller_ActionEventArgs))
#13 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Event/EventManager.php(214): Enlight_Event_Handler_Plugin->execute(Object(Enlight_Controller_ActionEventArgs))
#14 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Controller/Action.php(138): Enlight_Event_EventManager->notify('Enlight_Control...', Object(Enlight_Controller_ActionEventArgs))
#15 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Controller/Dispatcher/Default.php(523): Enlight_Controller_Action->dispatch('getShopsWithThe...')
#16 /var/www/vhosts/hundemarke.com/httpdocs/engine/Library/Enlight/Controller/Front.php(223): Enlight_Controller_Dispatcher_Default->dispatch(Object(Enlight_Controller_Request_RequestHttp), Object(Enlight_Controller_Response_ResponseHttp))
#17 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Kernel.php(178): Enlight_Controller_Front->dispatch()
#18 /var/www/vhosts/hundemarke.com/httpdocs/vendor/symfony/http-kernel/HttpCache/HttpCache.php(487): Shopware\Kernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#19 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Components/HttpCache/AppCache.php(255): Symfony\Component\HttpKernel\HttpCache\HttpCache->forward(Object(Symfony\Component\HttpFoundation\Request), true, NULL)
#20 /var/www/vhosts/hundemarke.com/httpdocs/vendor/symfony/http-kernel/HttpCache/HttpCache.php(258): Shopware\Components\HttpCache\AppCache->forward(Object(Symfony\Component\HttpFoundation\Request), true)
#21 /var/www/vhosts/hundemarke.com/httpdocs/engine/Shopware/Components/HttpCache/AppCache.php(103): Symfony\Component\HttpKernel\HttpCache\HttpCache->pass(Object(Symfony\Component\HttpFoundation\Request), true)
#22 /var/www/vhosts/hundemarke.com/httpdocs/shopware.php(113): Shopware\Components\HttpCache\AppCache->handle(Object(Symfony\Component\HttpFoundation\Request))
#23 {main}
Time:	2017-02-15T13:29:42.206989+0100
Channel:	core
request:	{
    "uri": "/backend/base/getShopsWithThemes?_dc=1487161784370&page=1&start=0&limit=1000&filter=%5B%7B%22property%22%3A%22main%22%2C%22value%22%3Anull%2C%22operator%22%3Anull%2C%22expression%22%3Anull%7D%5D",
    "method": "GET",
    "query": {
        "_dc": "1487161784370",
        "page": "1",
        "start": "0",
        "limit": "1000",
        "filter": "[{\"property\":\"main\",\"value\":null,\"operator\":null,\"expression\":null}]",
        "module": "backend",
        "controller": "base",
        "action": "getShopsWithThemes"
    },
    "post": []
}
shop:	No shop data available
session:	{
    "userId": "53",
    "roleId": "1"
}

Weiss jemand Rat, um was für ein Problem es sich handelt? Besten Dank schon Mal für die Antworten.