WFM API 409 Conflict during Zendesk Agent Group Migration?

Context:
Environment: Genesys Cloud 2024-10, Partner Org Context via AppFoundry Premium App
Integration: Bi-directional sync between Zendesk Support and Genesys WFM
Endpoint: POST /api/v2/wfm/userschedulesegments

Question:
Does anyone know why we are receiving a 409 Conflict error when attempting to create user schedule segments for agents migrated from Zendesk? The request body matches the schema exactly, yet the API rejects it with a generic conflict message, suggesting a hidden constraint or data mismatch in the partner org context.