POSTing to airtable through custom code and web service actions

I’m working on a project that requires that responses from Qualtrics Surveys get logged in airtable. I keep encountering this mysterious error when I try to create a record via POST. Any advice or direction you might be able to share would be greatly appreciated! I’ve been trying to solve this for almost three days now.
First I create a JSON object formatted according to the api’s specifications in a code task after the response is recorded, then pass that JSON object to the web service to POST to airtable
Here’s the full message I get from Qualtrics when I attempt to write to airtable:
> Input Payload
> {
> "payload": {
> "Fire": true,
> "pipedTextConfig": [],
> "exportMappings": [],
> "customSaveHandler": true,
> "taskNumber": 2,
> "elementConfigured": true,
> "createdAt": 1616820644283,
> "updatedAt": 1616832335963,
> "triggerAction": "WebService",
> "requestType": "POST",
> "contentType": "JSON",
> "url": "https://api.airtable.com/v0/appg---------------------------",
> "textPayload": "{\\"records\\":[\\"~{ch://OCAC_2Qxm6xaGnwmHtfI/fields}\\"],\\"typecast\\":\\"true\\"}",
> "name": "Token",
> "summary": "Authenticate with an access key",
> "id": "PLUG_d4015baa-9716-4aaa-a26c-45cdd460f081",
> "taskRegistryId": "APP_42a7f4b6-bb84-4c66-94cc-e3e1208e62bf",
> "actionId": "OCAC_Xj45GqNFvP9NW6J",
> "icon": "https://www.xm-apps-static.com/assets/v1/APP_42a7f4b6-bb84-4c66-94cc-e3e1208e62bf/1.0.27/2tl04rGNWIx8qbmr/images/logo-small.png",
> "contextId": "SV_bPAsnaCYe1SYKmq",
> "outcomeId": "OC_2CCX3dfIcEIfKIE",
> "surveyId": "SV_bPAsnaCYe1SYKmq",
> "Type": "OutcomeAction",
> "currentPipedTextTestMappings": {
> "~{ch://OCAC_2Qxm6xaGnwmHtfI/fields}": ""
> },
> "credentials": {
> "credentialId": "CRED_WwQTbyqDMWcYyk",
> "name": "volunteers",
> "scheme": "apikey"
> },
> "ownerObject": {
> "orgId": "berkeley",
> "userId": "UR_eh9TkyjopJ1LOsd"
> },
> "keyValues": {
> "typecast": "true",
> "records": [
> "~{ch://OCAC_2Qxm6xaGnwmHtfI/fields}"
> ]
> },
> "pipedTextImports": {
> "url": [],
> "headers": [],
> "body": [
> "~{ch://OCAC_2Qxm6xaGnwmHtfI/fields}"
> ]
> },
> "exports": [
> {
> "key": "headers",
> "display_name": "Headers"
> },
> {
> "key": "statusCode",
> "display_name": "Status Code"
> },
> {
> "key": "data",
> "display_name": "Data"
> }
> ],
> "dependencies": {
> "OCAC_2Qxm6xaGnwmHtfI": [
> "fields"
> ]
> },
> "headers": {
> "Content-Type": "application/json",
> "Authorization": "Bearer {{CRED_WwQTbyqDMWcYyk}}"
> },
> "chain": {
> "OCAC_2Qxm6xaGnwmHtfI": {
> "fields": {
> "Email": "erinkraemer@berkeley.edu",
> "ResponseId": "R_0JqkYtbDgYRUwP7",
> "First": "first",
> "Last": "last",
> "State": "California",
> "County": "orange",
> "Race": [
> "White"
> ],
> "RaceOther": "White",
> "Phone": "6504683045",
> "Languages": [
> "Armenian",
> "Bengali",
> "Cantonese",
> "English"
> ],
> "Roles": [
> "Vaccine Appointment Sleuth",
> "Community Outreach"
> ],
> "Source": "ok",
> "Certificate": "Yes",
> "CertificateCopy": "https://berkeley.qualtrics.com/WRQualtricsSurveyEngine/-----------------",
> "School": [
> "Yes at UC Berkeley"
> ],
> "Occupation": "ok",
> "Skills": "ok",
> "Notes": "oi"
> }
> }
> }
> },
> "data": {
> "eventTimestamp": 1616832428607,
> "throttleCount": 0,
> "uniqueId": "R_0JqkYtbDgYRUwP7",
> "contextId": "SV_---------------------",
> "workspaceId": "SV_------------------------",
> "workflowName": "Lets see if this workflow"
> },
> "user": {
> "userId": "UR_-----------sd",
> "brandId": "berkeley"
> },
> "notification": {
> "infos": [],
> "errors": []
> }
> }
>
> Task Output
> {
> "name": "ACTIONS.ERROR_CODES.INTERNAL_ERROR",
> "message": "{\\"error\\":{\\"type\\":\\"INVALID_REQUEST_UNKNOWN\\",\\"message\\":\\"Invalid request: parameter validation failed. Check your request d",
> "needRetry": false
> }