I'm having this same issue as well. After some digging around, in my instance, the error message is not being captured but occurs when Drupal tries to resolve Drupal\admin_toolbar_tools\Controller\ToolbarController in Drupal\Core\DependencyInjection\ClassResolver::getInstanceFromDefinition():
You have requested a non-existent service "search.search_page_repository"
I don't have search enabled on my site, but once I enable it, the error messages become a little more clear, since I haven't configured search, I just enabled the module:
The "search_page" entity type does not exist.
Once I cleared the cache via drush, the cache flush from the admin toolbar tools started working again.
Is it possibly an issue with an assumption that search will be enabled and configured fully?