ShippingOrderProcessor not registered well?
In this case, you'll want to run this before the commerce_shipping.early_order_processor, set priority to 300
services:
  shipping_fix.shipping_order_processor:
    class: Drupal\shipping_fix\ShippingProcessor
    arguments: ['@commerce_shipping.order_manager', '@commerce_shipping.shipment_manager']
    tags:
      - { name: commerce_order.order_processor, priority: 300 }