Issue with delete-participants API call in extension

For some reason I cannot get a “delete-participants” API call to work in my extension.

I can make other calls work, so it is not the connection or authentication. I keep on getting a 500 (internal server error), unless if I deliberately configure the body as a string instead of an array, then I get a 400 error.

I have tried all possible and impossible options to format the body, but a no point have I been successful in getting this to work from the extension. It is not a problem to get this to work from Postman, but running it from the extension just does not work.

This is the simplified code (with project ID hidden):

module.exports = async function(context) {
    let getDeleteParticipants;
    
    try {
        const requestOptionsDelete = {
            method: "POST",
            body: ["DisableTestID"],      
        };

        getDeleteParticipants = await context.client.qualtricsApiFetch('ex-projects/TS_……./delete-participants', requestOptionsDelete);

        if (error.status === 201){
            return {
                message: 'Job completed without any errors.',
                getDeleteParticipants: getDeleteParticipants,
                errorStatus: error.status
            };
        } else {
            return {
                message: 'Job failed.',
                getDeleteParticipants: getDeleteParticipants,
                errorStatus: error.status
            };
        }
        
    } catch (error){    

        return {
            message: 'Error happened.',
            getDeleteParticipants: getDeleteParticipants,
            errorStatus: error.status
        };
    }

};

And this is the output:

{  "actionId": "OCAC_ITu8fegq6eeSfFI",  "exports": {    "getDeleteParticipants": {      "responseData": {        "error": {          "errorCode": "DPG_0.0",          "errorMessage": "An unexpected error occurred."        },        "meta": {          "httpStatusCode": 500,          "requestId": "1798ee66-73eb-48db-8e9e-899b24702d6e"        }      },      "status": 500    },    "message": "Error happened."  }}

Can anyone make this work?