Rails project with ActionCable suddenly shows double Websocket connection

Question

I've been developing a quiz web application with Rails 5 and ActionCable and everything was working fine, but suddenly my browser started showing 2 'cable' websocket connections (and the logs also confirm that messages are sent twice).

What I'm talking about is this:

This is wholly unintentional on my part, but even after restarting the server and my PC and searching my code I don't get where the second connection comes from.

This is my connection.rb - standard for ActionCable:

module ApplicationCable
  class Connection < ActionCable::Connection::Base
    identified_by :current_user

    def connect
      self.current_user = find_verified_user
      logger.add_tags 'ActionCable', current_user
    end

    private
    def find_verified_user
      if verified_user = User.find_by(id: cookies.signed[:user_id])
        verified_user
      else
        reject_unauthorized_connection
      end
    end
  end
end

This is my routes.rb:

Rails.application.routes.draw do
  root to: redirect('teacher/home'), :role => "teacher", :page => "home"

  mount ActionCable.server => '/cable'
end

And this is the issue I was solving when the second connection started to appear. ^^*

I'd be happy for any ideas of where to look or what to do! :)