Don't Touch That Dial?
Did you ever head out for a shoot and start firing away? Thinkibng evertything is how you want it, because everything is how you left it? And then you chimp your shots and have a WTF moment, because they’re coming out like this:
* Author raises hand sheepishly *
It happens. Sometimes the settings get reset while the battery is out. Sometimes people touch your stuff and make changes. Sometimes, you have the SLR equivalent of a butt dial with the settings open.
The fix is simple enough. In this case ( some quick and dirty snapshots in a parking garage on AP), set the ISO to 100 (or whatever suits you) and shoot on. You may never know exactly why the ISO got flipped to auto, but at least now you’re in control, and not some electron-addled algorithm that thinks ISO 5000 would be a fun shake upright now.
TL;DR - Trust but verify. Do it with Camera settings, just like kid’s excuses and your available balance.