Data Action 500 Error During Zendesk Ticket Sync Migration

Looking for advice on why the Genesys Cloud Data Action returns a 500 Internal Server Error when mapping Zendesk ticket fields to interactions. The migration script works for simple text fields but fails on complex JSON structures.

{"errors":[{"code":"INTERNAL_SERVER_ERROR","message":"Failed to process data action input payload."}]}

Zendesk handles nested objects easily, but GC Admin Config seems to reject the payload format.