Setup:

APP_ENV=dev
APP_DEBUG=1

Steps to reproduce:

1. Login as admin
2. Go to "Page" -> "site"
3. Start creating a new Landing Page
4. Set required fields: Title and Description ("TestLP")
5. Add two Code Blocks with content: "Block1" and "Block2"
6. Save Landing Page Draft
7. Exit Landing Page editor by switching to view mode
8. Go to Admin -> Roles -> Anonymous
9. Delete the content/read policy from Anonymous role
10. Logout from all siteaccesses (I recommend closing the browser and opening a new private window)
11. Login as admin
12. From the Dashboard click the edit button next to "TestLP" in "Drafts" section"

Expected:

Page is rendered correctly

Actual:
Page Builder does not load.

Note:
I've noticed that I was not authenticated as admin user in EzSystems\EzPlatformPageFieldTypeBundle\Controller\BlockController::renderAction(), but a Anonymous instead.