Architect Flow 400 - Invalid JSON via Terraform

So I’m seeing a very odd bug with deploying a flow containing a custom data action. Provider v1.68.4. Region au-1. The HCL validates but the API rejects the step configuration.

resource “genesyscloud_flow” “test” { name = “test” }

Error: API request failed: 400 Bad Request. Details: Invalid JSON structure for custom_data_action.