Click & Drop integration and customs code

We have started using the click & drop integration for Shopify. Order value, postage value/type, item value, item name and weight are visible in click and drop and successfully captured from Shopify.

Customs code (which we have in Shopify) is not transferred to click and drop, which is a problem for our international orders. We are currently adding this information in manually. Does anyone have a suggestion for what we might be doing wrong?