Почему POST запрос выдает 400 ошибку?

Уважаемые коллеги, в чем может быть проблема?

      const checkboxes = {
    interactionId: this.interactionId,
    attributes: {
        accessServices: this.access.checked,
        processingPersonalData: this.personalData.checked,
        advertising: this.advertisingElement.checked,
        advertisingBank: this.advertisingBankElement.checked,
        smsMessage: this.smsElement.checked,
        photoVideoAudio: this.photoElement.checked,
        creditHistory: this.creditHistoryElement.checked,
        accessionService: this.accessionServiceElement.checked,
        accessionContract: this.accessionContractElement.checked,
        transmissionOthers: this.transmissionOthersElement.checked
    }
};
console.dir(checkboxes);

$.ajax({
   url: '/lalala/rest/offer',
   type: 'POST',
   data: JSON.stringify({   
    interactionId: this.interactionId,
        attributes: {
            accessServices: this.access.checked,
            processingPersonalData: this.personalData.checked,
            advertising: this.advertisingElement.checked,
            advertisingBank: this.advertisingBankElement.checked,
            smsMessage: this.smsElement.checked,
            photoVideoAudio: this.photoElement.checked,
            creditHistory: this.creditHistoryElement.checked,
            accessionService: this.accessionServiceElement.checked,
            accessionContract: this.accessionContractElement.checked,
            transmissionOthers: this.transmissionOthersElement.checked
        },
}),
   contentType: 'application/json; charset=utf-8',
   dataType: 'json'
})
   .done(resp => {
       if (resp.status === 'COMPLETED' &&
        (resp.reason === 'ERROR' || resp.reason === 'CANCEL_CANNOT_EXEC' || resp.resultInfo)
       ) {
        this.addErrorTemplate(resp);
       } else {
        this.notify('sfoRouteTask', {taskId: resp.id, layout: resp.type});
       }
   })
   .fail(() => this.notify('sfoError', 'Ошибка загрузки данных'));