[6.x] Losing data when creating new entries inside an entry

[tao]

Bug description

I have a collection called sections and the blueprint allows me to create and attach a list of subsections entries to it:

title: Section
tabs:
  main:
    display: Main
    sections:
      -
        fields:
          -
            handle: title
            field:
              type: text
              required: true
              localizable: true
              validate:
                - required
          -
            handle: subsections
            field:
              collections:
                - subsections
              type: entries
              display: Subsections
              localizable: false

When I am viewing the subsection History for example, and I use the button Create Entry it opens the slider and I try create a new entry like Photos... it looks like it works, it actually creates the subsection Photos in the content folder.

But when I hit the Save & Publish button it renames my section History -> Photos and doesn't attach the subsection.

How to reproduce

Here's the subsection blueprint too:

title: Subsection
tabs:
  main:
    display: Main
    sections:
      -
        display: Content
        fields:
          -
            handle: title
            field:
              type: text
              required: true
              localizable: true
              validate:
                - required
          -
            handle: content
            field:
              type: markdown
              localizable: true
      -
        display: 'New Section'
  sidebar:
    display: Sidebar
    sections:
      -
        fields:
          -
            handle: slug
            field:
              type: slug
              localizable: true
              validate: 'max:200'

Both entries have slugs: false enabled on the collection it that might be causing an issue, but otherwise it's a brand new Statamic site for testing.

Logs

Environment

Statamic
Addons: 0
Sites: 28 (English, Arabic, Bulgarian, and 25 more)
Stache Watcher: Disabled (auto)
Static Caching: Disabled
Version: 6.0.0-alpha.15 PRO

Installation

Existing Laravel app

Additional details

No response

[tao]

missing.sections.mov

In the video you can see I have my section called "How the Ra Contact Came to Be" with the ID in the URL "4e34f280-etc" and I just refreshed the page so the current subsection has already been saved. Then I create a new subsection and when I save, it removes both the title and existing subsection.

And at the end you can see the ID in the URL is the same but now it has the name of the new subsection I tried to create.

You can even see in the video before it reloads, it kind of flashes the new title before going back to the entries list screen.