Comment notification on group stream does not disappear after comment deletion

While the comment is gone, the notification on the group page about this comment is still there and there is no way to delete it.
To recreate it, comment on anything on the group and then try to delete the comment.
While trying to recreate the issue I tried to delete another comment and got a blank page with this error:
{
"message": "The \"comment\" parameter was not converted for the path \"/ajax_comments/{comment}/delete\" (route name: \"ajax_comments.delete\")"
}

Going back to the page and refreshing this comment actually disappeared. It will be nice not to have the error obviously, but at least this deletion does not leave un-deleted notification like the issue above.

uninstalling Social Ajax Comment and leaving Ajax Comment installed solved the second problem.

I still have the notification from the previously deleted comment still hanging on t he group's stream.
Any idea how to remove this notification?