Clean upgrade from 8.4.3 to 8.6.3

update.php – The website encountered an unexpected error. Please try again later.

Error in weblog:

[host www.more-it.dk] Backend log: ReflectionException: Class DrupalblockEventSubscriberBlockPageDisplayVariantSubscriber does not exist in /var/www/more-it.dk/public_html/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterEventSubscribersPass.php on line 30 #0 /var/www/more-it.dk/public_html/core/lib/Drupal/Core/DependencyInjection/Compiler/RegisterEventSubscribersPass.php(30): ReflectionClass->__construct(‘Drupal\block\Ev…’)n#1 /var/www/more-it.dk/public_html/vendor/symfony/dependency-injection/Compiler/Compiler.php(141): DrupalCoreDependencyInjectionCompilerRegisterEventSubscribersPass->process(Object(DrupalCoreDependencyInjectionContainerBuilder))n#2 /var/www/more-it.dk/public_html/vendor/symfony/dependency-injection/ContainerBuilder.php(788): SymfonyComponentDependencyInjectionCompilerCompiler->compile(Object(DrupalCoreDependencyInjectionContainerBuilder))n#3 /var/www/more-it.dk/public_html/core/lib/Drupal/Core/DrupalKernel.php(1322): SymfonyComponentDependencyInjectionContainerBuilder->compile()n#4 /var/www/more-it.dk/public_html/core/lib/Drupal/Core/DrupalKernel.php(896): DrupalCoreDrupalKernel->compileContainer()n#5 /var/www/more-it.dk/public_html/core/lib/Drupal/Core/DrupalKernel.php(472): DrupalCoreDrupalKernel->initializeContainer()n#6 /var/www/more-it.dk/public_html/core/lib/Drupal/Core/DrupalKernel.php(668): DrupalCoreDrupalKernel->boot()n#7 /var/www/more-it.dk/public_html/index.php(19): DrupalCoreDrupalKernel->handle(Object(SymfonyComponentHttpFoundationRequest))n#8 {main}n

What to check for error?

Newbie!

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/21/feed