`No value present` when `receiveSyncMessage` twice with the same payload

Occurs for both identical and equal payloads.

To reproduce this, receive the same bytes sequence of bytes twice. A `NoSuchElementException` is raised from `Optional` somewhere in `receiveSyncMessage`. It seems that every message received after this occurs will be met with the same exception, new or not.

`generateSyncMessage` _seems_ to exhibit the same behavior after raising the exception in `receiveSyncMessage`, suggesting that there might be something stateful breaking after the exception occurs the first time.

Start at receiveSyncMessage and compare its state handling with generateSyncMessage; reproduce the failure by processing the same byte sequence twice and inspect the Optional path that raises NoSuchElementException. Done means identical and equal payloads can be processed repeatedly without poisoning later receiveSyncMessage or generateSyncMessage calls, with regression coverage for both cases.

Written by the indexing model from the issue text.