Custom metric/dimension not visible in GA4 DebugView on item/product-list level

Question

We're trying to configure GA4 to gather same data that we have in UA.

The problem is that we cant see custom metrics data on item-level in DebugView. In TagAssistant we can see that data is sent:

{
  event: "purchase",
  gtm: {uniqueEventId: 10, start: 1651XXX},
  gtag: {
    targets: {
      G-XXX: {_ee: true, _uei: 3, _upi: 2},
      UA-XXX: {
        currency: "PLN",
        country: "PL",
        custom_map: {
          dimension2: "referrer",
          ...
          dimension13: "ecomm_totalvalue",
          metric1: "metric1",
          ...
          metric5: "metric5"
        },
        _uei: 4
      },
      AW-106XXX: {}
    }
  },
  eventModel: {
    transaction_id: "40XXX",
    affiliation: "XXX",
    value: "9.99",
    currency: "PLN",
    tax: "1.87",
    shipping: "0",
    coupon: "",
    items: [
      {
        id: "670",
        name: "Tusz Zamiennik T0711 do Epson (C13T07114010) (Czarny)",
        brand: "XXX",
        category: "Wkłady/Atramentowe/Zamienniki/Tusze/XXX -> Do:E" +
                  "pson",
        quantity: 1,
        price: "9.99",
        coupon: "",
        metric1: "9.99",
        metric2: "9.99",
        metric3: "9.99",
        metric4: "9.99",
        metric5: "9.99"
      }
    ],
    send_to: ""
  }
}

However, on DebugView side we can see purchase event that:

• contains all orginal parameters on event level (like transaction_id, shipping etc.)
• contains all orginal parameters on item level (like item_id, quantity, etc.)

But our custom metrics are missing

In the other hand, we tried (with different event) push some custom-dumension data and:

• they are visible on GA4 DebugView
• we can create custom dimension in GA4 basing on this data and it works

I am thinking about:

1. Creating event-level custom metric to test if it will be passed to GA4 DebugView
2. Creating item-level custom dimension to test if it will be passed to GA4 DebugView

However, due to fact that GA requires 24h to make conclusions i decided to ask here for any sugestions why it is not working and what else may i test.