Ecommerce framework - error saving products after platform update

After updating to Pimcore version 6.3.6 (from 6.1) I get the following error each time I try to “save&publish” a product. Did someone already found a similar problem?

Status: 500 | Internal Server Error
URL: /admin/object/save?task=publish
Method: PUT
Message: Argument 1 passed to “Symfony\Component\EventDispatcher\EventDispatcherInterface::dispatch()” must be an instance of Symfony\Component\EventDispatcher\Event, Pimcore\Event\Model\Ecommerce\IndexService\PreprocessAttributeErrorEvent given.
Trace:
in /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/Debug/TraceableEventDispatcher.php:154
#0 /var/www/sphera/vendor/pimcore/pimcore/bundles/EcommerceFrameworkBundle/IndexService/Worker/AbstractBatchProcessingWorker.php(238): Symfony\Component\EventDispatcher\Debug\TraceableEventDispatcher->dispatch(Object(Pimcore\Event\Model\Ecommerce\IndexService\PreprocessAttributeErrorEvent), Object(Pimcore\Event\Model\Ecommerce\IndexService\PreprocessAttributeErrorEvent))
#1 /var/www/sphera/vendor/pimcore/pimcore/bundles/EcommerceFrameworkBundle/IndexService/Worker/OptimizedMysql.php(95): Pimcore\Bundle\EcommerceFrameworkBundle\IndexService\Worker\AbstractBatchProcessingWorker->prepareDataForIndex(Object(AppBundle\Model\DefaultProduct))
#2 /var/www/sphera/vendor/pimcore/pimcore/bundles/EcommerceFrameworkBundle/IndexService/IndexService.php(181): Pimcore\Bundle\EcommerceFrameworkBundle\IndexService\Worker\OptimizedMysql->updateIndex(Object(AppBundle\Model\DefaultProduct))
#3 /var/www/sphera/vendor/pimcore/pimcore/bundles/EcommerceFrameworkBundle/EventListener/IndexUpdateListener.php(40): Pimcore\Bundle\EcommerceFrameworkBundle\IndexService\IndexService->updateIndex(Object(AppBundle\Model\DefaultProduct))
#4 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/Debug/WrappedListener.php(126): Pimcore\Bundle\EcommerceFrameworkBundle\EventListener\IndexUpdateListener->onObjectUpdate(Object(Pimcore\Event\Model\DataObjectEvent), ‘pimcore.dataobj…’, Object(Symfony\Component\HttpKernel\Debug\TraceableEventDispatcher))
#5 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/EventDispatcher.php(260): Symfony\Component\EventDispatcher\Debug\WrappedListener->__invoke(Object(Pimcore\Event\Model\DataObjectEvent), ‘pimcore.dataobj…’, Object(Symfony\Component\HttpKernel\Debug\TraceableEventDispatcher))
#6 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/EventDispatcher.php(235): Symfony\Component\EventDispatcher\EventDispatcher->doDispatch(Array, ‘pimcore.dataobj…’, Object(Pimcore\Event\Model\DataObjectEvent))
#7 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/EventDispatcher.php(73): Symfony\Component\EventDispatcher\EventDispatcher->callListeners(Array, ‘pimcore.dataobj…’, Object(Pimcore\Event\Model\DataObjectEvent))
#8 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/EventDispatcher/Debug/TraceableEventDispatcher.php(168): Symfony\Component\EventDispatcher\EventDispatcher->dispatch(Object(Pimcore\Event\Model\DataObjectEvent), ‘pimcore.dataobj…’)
#9 /var/www/sphera/vendor/pimcore/pimcore/models/DataObject/AbstractObject.php(694): Symfony\Component\EventDispatcher\Debug\TraceableEventDispatcher->dispatch(Object(Pimcore\Event\Model\DataObjectEvent), Object(Pimcore\Event\Model\DataObjectEvent))
#10 /var/www/sphera/vendor/pimcore/pimcore/models/DataObject/Concrete.php(741): Pimcore\Model\DataObject\AbstractObject->save(Array)
#11 /var/www/sphera/src/AppBundle/Model/DefaultProduct.php(41): Pimcore\Model\DataObject\Concrete->save()
#12 /var/www/sphera/vendor/pimcore/pimcore/bundles/AdminBundle/Controller/Admin/DataObject/DataObjectController.php(1318): AppBundle\Model\DefaultProduct->save()
#13 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/HttpKernel.php(151): Pimcore\Bundle\AdminBundle\Controller\Admin\DataObject\DataObjectController->saveAction(Object(Symfony\Component\HttpFoundation\Request))
#14 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/HttpKernel.php(68): Symfony\Component\HttpKernel\HttpKernel->handleRaw(Object(Symfony\Component\HttpFoundation\Request), 1)
#15 /var/www/sphera/vendor/symfony/symfony/src/Symfony/Component/HttpKernel/Kernel.php(198): Symfony\Component\HttpKernel\HttpKernel->handle(Object(Symfony\Component\HttpFoundation\Request), 1, true)
#16 /var/www/sphera/web/app.php(36): Symfony\Component\HttpKernel\Kernel->handle(Object(Symfony\Component\HttpFoundation\Request))
#17 {main}

This is my current configuration:


Symfony


Version 4.3.11
End of maintenance 01/2020 Expired
End of life 07/2020


Kernel


Type AppKernel
Environment prod
Debug false
Charset UTF-8
Cache directory ./var/cache/prod (11.9 MiB)
Log directory ./var/logs (194.4 MiB)


PHP


Version 7.2.24-0ubuntu0.19.04.2
Architecture 64 bits
Intl locale en_US
Timezone Europe/Berlin (2020-04-22T12:10:29+02:00)
OPcache true
APCu false
Xdebug false