When the "Hide the header in zenmode" option is enabled (which it is by default) but the notebook's header is already hidden before zenmode is entered, then the headers will be shown when zenmode exits. Additionally, the "View > Toggle Header" menu item must then be selected twice to hide the header again.
I think zenmode needs to check the visibility of the header when it is entered and save that state for later use. If the header is already hidden, zenmode shouldn't try to hide it. Likewise, later when zenmode exits, if the header was initially hidden, zenmode shouldn't try to show it.
I haven't tested it, but I wouldn't be surprised if this also applied to the menubar hiding option, too.
When the "Hide the header in zenmode" option is enabled (which it is by default) but the notebook's header is already hidden before zenmode is entered, then the headers will be shown when zenmode exits. Additionally, the "View > Toggle Header" menu item must then be selected twice to hide the header again.
I think zenmode needs to check the visibility of the header when it is entered and save that state for later use. If the header is already hidden, zenmode shouldn't try to hide it. Likewise, later when zenmode exits, if the header was initially hidden, zenmode shouldn't try to show it.
I haven't tested it, but I wouldn't be surprised if this also applied to the menubar hiding option, too.