We recently updated devices in the cros lab from .149 -> .157 and some of them didn't boot back into OS after the subsequent reboot, eg:

https://luci-milo.appspot.com/buildbot/chromeos/kevin-paladin/292


02/24 10:49:01.993 INFO |     cros_firmware:0291| Updating firmware from Google_Kevin.8785.149.0 to Google_Kevin.8785.157.0
02/24 10:49:01.994 DEBUG|          ssh_host:0284| Running (ssh) 'chromeos-firmwareupdate --mode=autoupdate'
02/24 10:49:03.566 DEBUG|        base_utils:0280| [stdout] Starting Google_Kevin firmware updater v5 (autoupdate)...
02/24 10:49:03.567 DEBUG|        base_utils:0280| [stdout]  - Updater package: [Google_Kevin.8785.157.0 / EC:kevin_v1.10.169-1cffa00]
02/24 10:49:03.567 DEBUG|        base_utils:0280| [stdout]  - Current system:  [RO:Google_Kevin.8785.135.0 , ACT:Google_Kevin.8785.149.0 / EC:kevin_v1.10.156-1ac8d3e]
02/24 10:49:03.749 DEBUG|        base_utils:0280| [stdout]  - Write protection: Hardware: off, Software: Main=off
02/24 10:49:03.886 DEBUG|        base_utils:0280| [stdout]  * invoke: flashrom -p host  -r _current/bios.bin
02/24 10:49:11.075 DEBUG|        base_utils:0280| [stdout]  * invoke: flashrom -p host --fast-verify -w bios.bin -i RW_SECTION_A
02/24 10:49:19.501 DEBUG|        base_utils:0280| [stdout] On reboot EC update may occur.
02/24 10:49:19.501 DEBUG|        base_utils:0280| [stdout] Firmware update (autoupdate) completed.

... but we fail to come back after reboot.

02/24 11:00:59.719 ERROR|     cros_firmware:0299| chromeos-firmwareupdate failed: from Google_Kevin.8785.149.0 to Google_Kevin.8785.157.0

This might be related to issue chrome-os-partner:62439.