After updating my core with 8.6.15 and devel with 8.2 version, I am facing the following error:
Route "devel.toolbar.settings_form" does not exist.
The website encountered an unexpected error. Please try again later. Symfony\Component\Routing\Exception\RouteNotFoundException: Route "devel.toolbar.settings_form" does not exist. in Drupal\Core\Routing\RouteProvider->getRouteByName() (line 201 of core/lib/Drupal/Core/Routing/RouteProvider.php). Drupal\Core\Routing\UrlGenerator->getRoute('devel.toolbar.settings_form') (Line: 271)