POST to Zapier Webhook only works 33-50% of the time

I’m trying to send data to Zapier’s webhook but it doesn’t seem to go through every single time. I’m a coding newbie, is there some sort of naive mistake I’m making below?

let result = new XMLHttpRequest();
let webhookURL = "https://hooks.zapier.com/hooks/catch/XXXXXX/YYYYY/";
let data = {
    "id" : record.id,
    "Format" : {name: record.getCellValueAsString("Format")}
};
await result.open("POST", webhookURL, true);
await result.setRequestHeader('Content-type','application/x-www-form-urlencoded');
await result.send(JSON.stringify(data));

I’ve noticed that it seems to make a difference if I have this command near the top of my script vs near the bottom.