Hello,
Posting this here for awareness.
I've discovered that on newer non-touchscreen Edge devices, like Edge 530 (which I own), if you access the In App settings menu from a Connect IQ app where that In App Settings menu contains more than a screen full of menu items, and you access a menu item scrolled off the screen, when returning back from that menu item and you press the "UP" button, the device will restart, every time. It appears the menu has lost focus returning from a menu item that was off the screen. I'm not sure if this is also a problem with touch screen devices (I don't have one), but I suspect it's not. This problem is not re-producible in the Connect IQ simulator (it behaves as you would expect there), only reproducible on an actual device.
I don't know whether this is a device firmware issue, or a connect IQ SDK issue. I have logged a bug (with test code that reproduces the problem), here:
One could argue this is quite a specific case that might not impact many people or devices and that may be so, but the fact it triggers a device restart is quite serious (to me at least) and although the testing I did found that any running activity was not lost, there is no guarantee that will always be the case.