Duplicate posts doesnt duplicate the metafields of jetengine

That’s because the new custom meta storage uses a custom DB table to store the custom field values. ASE only works with custom field values stored in the default wp_postmeta table, like most other “post duplication” plugins. You’d need to ask JetEngine support on which post duplication plugin works with their custom meta storage option, or, ask them to implement a post duplication feature inside JetEngine that works with it.