Currently custom line items are not supported with Managed Markets and custom line item properties.
https://help.shopify.com/en/manual/international/managed-markets/fulfillment
You will need to contact Shopify to fix this issue on their end.
https://help.shopify.com/en/questions#/contact
Sorry we couldn’t be more helpful, this is a limitation of Shopify.
Custom line items are what our app uses to add our virtual option selections.