Session request submission fails with error

Submitting a session request from the Request page fails with the error 'Unable to Submit session. Please try again.' after the full form is completed. The error appears as a toast notification at the 'Finalize & submit' step of the request flow. The failure has persisted across multiple days, and the session cannot be saved as a draft either, so there is no way to preserve or resubmit the request. Investigate the submission endpoint and draft-saving path for session requests.