Unexpected response after failed session command

In certain corner cases where a read-only transaction involves session commands and the routing of the session command to the primary server fails, an unexpected response from the read-only transaction's target server may be received. This happens for two reasons: the failure is treated as retryable when it should not be and a failed write to the the current primary server is treated as a failure instead of treating the failed write to the session command replier as the failure.

In practice it is very hard for these conditions to be met and the failure can only be reproduced in multi-level configurations with pipelined commands.