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E65 — WS_PACKET_SERIALIZE_FAILED

A packet the device tried to send could not be serialised to JSON.

What happens​

The packet is silently dropped — it is never sent to the server. The error is logged once per boot. The WebSocket connection and all other operations continue normally.

Possible causes​

  • Heap allocation failed during JSON serialisation. This can happen if the heap is severely fragmented after a long session or after recovering from a crash.
  • A firmware bug caused invalid data to be placed in the packet fields (e.g., a non-finite float).

How to fix​

  1. Reboot the device — Resets the heap. If this was a one-off allocation failure it will not recur.
  2. Update the firmware — Newer firmware may reduce peak heap usage during serialisation.
  3. Contact support — Open an issue on GitHub if this appears consistently, especially if it coincides with missing solve submissions.