[wp-trac] [WordPress Trac] #52446: Issue with custom post types and classic editor - "Changes you made may not be saved"

[WordPress Trac]

#52446: Issue with custom post types and classic editor - "Changes you made may not
be saved"
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 Reporter:  tonysandwich  |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Since upgrading yesterday to 5.6.1, any time I try to edit a custom post
 type without the Gutenberg editor enabled in the supports array of the
 custom post type I get a "Changes you made may not be saved" alert, even
 if I did not make any changes, or even if the post has been published.

 Enabling Gutenburg in supports fixes this issue, however if I enable the
 Gutenburg editor, and then install the classic editor plugin I get the
 same alert each time I try and navigate away from the post editor screen.

 I have reverted back to 5.6 and everything works as it should.

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Ticket URL: <https://core.trac.wordpress.org/ticket/52446>
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