Trying to setup UTM parameters on a clients Wix site with form v2 and keep receiving “…type does not exist in FormValues”

I have spent so many hours just trying to figure out why Velo cannot recognize my form field key/field title to assign a utm parameter to the field… and no I am not misspelling the field key or getting it wrong. The goal here is to take a utm parameter from an ad campaign and place it into a hidden empty field within the Wix v2 Form.

The code below should taking the utm parameter utm_source from the URL, then locates the form called #djform which is located on the page, and then it should be calling setFieldValues to insert the value from the custom parameter utm_source into the hidden empty field which is called utmsource_1

I keep receiving this exact error:

Argument of type ‘{ utmsource_1: string; }’ is not assignable to parameter of type ‘FormValues’. Object literal may only specify known properties, and ‘utmsource_1’ does not exist in type ‘FormValues’.

import wixLocationFrontend from 'wix-location-frontend';

$w.onReady(function() {

    const query = wixLocationFrontend.query;
    let utmSource = decodeURIComponent(query.utm_source).toString();

    // // Use direct element ID references to set values
    if (query.utm_source) {
        $w('#djform').setFieldValues({
        utmsource_1: utmSource,
        });
    }
});

For some reason Velo can’t recognize utm_source1 when I’m trying to set that hidden Field Value to a specified utm parameter… the Field Value should be what is essentially an element ID or in this case, a Field Key

Here is the setFieldValues documentation from Velo – https://dev.wix.com/docs/velo/api-reference/$w/wix-forms-v2/set-field-values