When an Admin modified a Post via Quick Edit mode, the original author is removed and the logged in username is linked.
If I disable the plugin, it works how it suppose to.
I tried to fix the bug.
I commented the
add_action( 'load-edit.php', array( $this, 'remove_quick_edit_authors_box' ) );
line in co-authors-plus.php file and the bug is gone.
Except, you cannot use the Author dropdown in Quick Edit mode to change authors. You must Full Edit the Post to change authors.
I'm wondering, if anybody could come up with hiding the author dropdown in Quick Edit mode and still maintain the original author. That would be perfect fix.
I hope the authors of this plugin can release a fix fast.