When a write command with ordered: false runs inside a multi-document transaction and the router fails to target one of its operations with a transient error, mongos returns the failure as a per-operation write error in an ok: 1 reply, with no errorLabels field.

Because the TransientTransactionError label is missing, neither drivers nor the shell's retry helpers recognize the failure as retryable, so a benign and self-healing race is surfaced to the application as a permanent write failure.

The equivalent ordered: true command does not have this problem: it fails the whole command and the reply is labelled TransientTransactionError as expected.