The Play Console has a bug and that's why it doesn't work. This is the work around:
Say, you have two versions:
- Beta: 29
- Alpha: previously version 29, but now empty: 'Promoted to beta’ it says. You want to upload version 30.
Then do this:
- Create a new Alpha release with version 30, and deactivate the previous APK. When you try to roll it out, it errors Fully shadowed APK.
- Go back a page and now remove version 30. Version 29 will be selected, click Save and Start roll out to Alpha. This only deactivates 29.
- Create a new Alpha release for 30, it should work now.