We recently had a power outage in an area of our plant affecting 4 of our controllers, 3 restarted fine as I expected but one came back and showed up as having no configuration (yellow triangle). As far as I can tell they are all configured the same for cold restart, and they all lost power for the same amount of time. I did a total download of the controller and it seems to be working fine now, I'm just wondering what could cause this and if it is a symptom of a bad controller that we should plan to replace later. We are running version 8.4.2