Not working from inside engine controller

[JakeTheSnake3p0]

I want to cache my http status response pages, and I use my mountable engine to generate those pages for each of my applications. The problem is that nothing gets cached. I've verified that the controller method is being executed as I actually do get the fully generated HTML response; it's just that the file isn't saved to /public. You'll note below that I attempt to log the public directory inside the page_cache_directory proc but I don't see any logs written either.

Main app:

config/application.rb: config.exceptions_app = routes

---

Engine:

lib/manager/engine.rb: (don't know for sure if this is what I need to require, so I tried both)

require 'actionpack/page_caching'
require 'action_controller/page_caching'

Routes:

%w(401 403 404 410 422 500).each do |code|
  get code, to: 'errors#show', as: "error_#{ code }", code: code
end

ErrorsController:

require_dependency 'manager/application_controller'
module Manager
  # Raise templated HTTP response pages
  class ErrorsController < ApplicationController
    skip_before_action :login_required
    skip_before_action :find_model

    self.page_cache_directory = -> { Rails.logger.debug Rails.root.join('public').inspect; return Rails.root.join('public') }
    caches_page :show

    def show
      render_status params[:code]
    end

    protected

    def render_status(status = 500)
      status = status.to_i
      respond_to do |format|
        format.any(:html, :shtml) do
          render "#{ status }.html", status: status
        end
      end
    rescue ActionController::UnknownFormat, ActionView::MissingTemplate
      head status: status
    end
  end
end

I also call caches_page directly in one of the main application's controller and it works. It's just from within the rails engine that it doesn't.