So I’m seeing a very odd bug with a Data Action configured to update a custom object via a REST API integration. The flow executes successfully in the Architect debug mode, yet the production logs consistently record a 400 Bad Request response. The integration is mapped to a standard POST endpoint expecting a JSON body. The request headers include the correct Authorization Bearer token and Content-Type set to application/json. The issue appears isolated to specific payload structures containing nested arrays. When the payload is simplified to a flat key-value pair, the action succeeds without error. This suggests the platform’s JSON serialization engine may be mishandling complex object hierarchies during the data action execution phase. The error response body returns a generic message indicating invalid syntax, which provides no actionable insight into the specific malformed character or structure. We are operating in the Europe/Paris timezone, and the server timestamps on the failed requests align with peak business hours, suggesting potential load-related serialization failures, although this remains speculative. The data action is triggered from a voice flow after collecting customer preferences via a form. The form data is mapped directly to the data action inputs. The platform documentation states that complex objects should be serialized automatically, but the behavior observed contradicts this expectation. The specific error trace shows the failure occurs at the request dispatch stage, not during the response parsing. This indicates the outbound request itself is malformed. We have verified the target API accepts the exact payload structure via Postman, ruling out backend validation issues. The problem persists across multiple tenant environments. We need clarity on whether there are known limitations regarding nested JSON structures in Data Actions or if a specific configuration flag is required to enable deep object serialization. The current behavior is blocking the deployment of a critical customer preference update flow. Any guidance on configuring the data action to handle complex payloads correctly would be appreciated. The goal is to ensure reliable data synchronization without manual intervention or flow redesign. The business impact is significant as this affects customer retention metrics tracked via the performance dashboards. We require a definitive solution or a workaround to bypass the serialization limitation. The platform version is current as of the last major update. The integration uses standard OAuth 2.0 for authentication. The endpoint supports HTTPS only. The timeout settings are default. The retry logic is disabled for this test. The logs show no network errors. The issue is strictly related to payload formatting. We have exhausted basic troubleshooting steps. We are looking for expert input on platform behavior regarding JSON complexity in data actions.