Missing custom fields while import site data

I use WP Importer 0.6.3 and also in my theme there are menu structure that has some custom fiels for every munu point like “Anchor”, “Icon” and so on. If i export all site data with WP Importer i can see menu and menu fields inside XML like this:

<wp:postmeta>
	<wp:meta_key><![CDATA[_menu_item_anchor]]></wp:meta_key>
	<wp:meta_value><![CDATA[qqqqqq]]></wp:meta_value>
</wp:postmeta>

But after import this xml back into site i have correct menu and menu items, but all custom fileds is empty, beside Navigation Label and Title Attribute.
This bug appears to be in WP 4.6