Save State Not Remembered After Browser Refresh

Hi

I have added the following field group e.g. code below. when I enable the 'save_state' => true the state of the expanded or collapsed state is not remembered when refreshing the browser. I have tried Firefox and Chrome browsers and it always reverts back to the default_state but even if I remove this then it still does not work.

[
	'type' => 'group',
	'id'   => 'packaging',
	'name' => 'product size and weight',
	'group_title' => 'Packaging',
	'clone' => false,
	'collapsible' => true,
	'default_state' => 'collapsed',
	'save_state' => true,
	'fields' => [
		[
			'type'  => 'number',
			'name'  => 'Height',
			'id'    => 'product_height',
			'step'  => '.01', 
			'placeholder'  => '',
			'append'  => self::$productUnit,
			//'min'  => '0',
			//'max'  => '10000',
			'sanitize_callback' => 'absfloat',
			'required' => false,
			'columns'  => 6,
		],
	]
]