I am trying to send a web-push subscription object to my API, which consists of 'endpoint' and 'keys'.

The problem I seem to be having is when this object reaches my API it has the 'Keys' values but the 'endpoint' value is null. Yet when I debug it I can confirm that the endpoint value is defined.

This is the JS code I am using:

async function Subscribe() {
        let sw = await navigator.serviceWorker.ready;
        let push = await sw.pushManager.subscribe({
            userVisibleOnly: true,
            applicationServerKey:
                'ApplicationServerKeyHere'
        });
        console.log(JSON.stringify(push)); //Store this in DB

        fetch("https://localhost:44325/Subscribe", {
            method: "POST",
            //credentials: "same-origin", // include, *same-origin, omit
            headers: {
                "Content-Type": "application/json"
            },
            body: JSON.stringify(push)
        });
    }

endpoint is populated before the Fetch POST is sent:

And then empty when it arrives at the API: