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E41 — OTA_MARK_VALID_FAILED

The firmware failed to mark itself as valid in the OTA state partition after an update.

What happens​

The error is logged and boot continues normally. The failure is non-fatal for the current session. However, because the OTA slot was not marked valid, the bootloader may roll back to the previous firmware on the next reboot.

Possible causes​

  • A flash write error occurred while marking the slot (worn flash cell, brief power interruption).
  • The OTA state partition is corrupted.

How to fix​

  1. Trigger another OTA update — A successful update will correctly mark the new slot as valid.
  2. Reflash via USB — Connect the device via USB and use espflash to flash the firmware directly. This bypasses OTA and resets the OTA state.
  3. Contact support — If this error appears after every OTA update, open an issue on GitHub.