Device bricked ("csum err") after two months of service

[PanicanWhyasker]

The engine signal is optoisolated in the new revision. Also its conditioning circuitry is moved off to a small PCB, separate from the main PCB which has the ESP.

[phatpaul]

Hi,
I see a similar issue with bootloader corruption. Please see my issue: viewtopic.php?f=12&t=13750

Did you ever find the root cause?

[PanicanWhyasker]

Sorry, I guess I'm not helping much here (answering a 9-month old question).
The root cause was never found out, but my best guess is that the high EMI noise near the ICE was the culprit and it was causing the flash chips (Winbond W25Qxxx) to execute something stupid, like to partly erase a block of the bootloader. Exact mechanism of this is unknown, though. Could be a corrupted command ESP->Flash caused by the interference, but who knows?