[Ovmsdev] What causes factory reset?

This evening I connected my new OVMS v3.1 to my laptop and went through the setup wizard. That seemed to go smoothly. I copied over my ssh key and things seemed to be working fine. I installed an SD card so I could do logging if needed, and then unplugged the module to install it in the car. But it didn't come up! After I brought it back to the desk and connected to the laptop again, I see a message on the console that it has factory reset itself. What are the ways to trigger a factory reset? I must have unintentionally hit one. -- Steve