Had an interesting one with a Voyager at New St last year during engineering works. It had terminated at New St and sat idling. However I think it had been left for the best part of an hour and eventually it inevitably went Eco. In doing so, all that worked were a few lights and the PA (TM used it to apologise and advised we'd have to wait for the driver to restart it) - even the internal and external doors no longer worked!
Driver restarted it but one of the engines decided to not play ball (having been working before) and we proceeded an engine down (5 car so no performance hit, just quiet!)