Subscription to metaobjects webhooks not working

Webhooks and Events
1

Our application is subscribing to metaobjects create, update and delete topics but although we can see the subscriptions have been registered the application is not receiving webhooks for the metaobjects for the type used in the filter. This is on a test store using API version 2025-07.

This is the mutation used to subscribe:

mutation
            {
                webhookSubscriptionCreate (topic: METAOBJECTS_CREATE, webhookSubscription: {
                                                                                callbackUrl: "https://test.ngrok.dev/shopify/webhook",
                                                                                includeFields: ["id", "updated_at"]
                                                                                filter: "type:metaobjdef"
                                                                              }) 
                {
                    webhookSubscription {
                        id
                    }
                }
            }

This is the active subscription:

       {
          "id": "gid://shopify/WebhookSubscription/1358964457551",
          "topic": "METAOBJECTS_CREATE",
          "includeFields": [
            "id",
            "updated_at"
          ],
          "filter": "type:metaobjdef",
          "endpoint": {
            "__typename": "WebhookHttpEndpoint",
            "callbackUrl": "https://test.ngrok.dev/shopify/webhook"
          }
        },
        {
          "id": "gid://shopify/WebhookSubscription/1358964490319",
          "topic": "METAOBJECTS_UPDATE",
          "includeFields": [
            "id",
            "updated_at"
          ],
          "filter": "type:metaobjdef",
          "endpoint": {
            "__typename": "WebhookHttpEndpoint",
            "callbackUrl": "https://test.ngrok.dev/shopify/webhook"
          }
        },
        {
          "id": "gid://shopify/WebhookSubscription/1358964523087",
          "topic": "METAOBJECTS_DELETE",
          "includeFields": [
            "id"
          ],
          "filter": "type:metaobjdef",
          "endpoint": {
            "__typename": "WebhookHttpEndpoint",
            "callbackUrl": "https://test.ngrok.dev/shopify/webhook"
          }
        }

Are we missing anything?

Note that the app subscribes to other topics for which work as expcted. The only difference here is that for metaobjects the filter on type is required.