Predictive Outbound Strategy 422 during Terraform Apply in AU-1 BYOC

Struggling to figure out why the genesyscloud_predictive_outbound_campaign resource fails with 422 Unprocessable Entity during apply. The plan succeeds, but the API rejects the segment_id reference in the campaign configuration block. Running provider v1.3.1 in AU-1 BYOC. HCL structure matches the documentation exactly.