This is a weird one.
I'm using a device factory for the Ecobee 2 plugin device creation process. I'm creating multiple devices in closedDeviceFactoryUi(). Some devices are grouped into a device group (the thermostat and occupancy sensor, if present). I also create devices for linked remote sensors, if the user requests them. When the devices are first created, ALL of them show in the device group. After I close the dialog box, only the actual grouped devices are shown. So it's grouping them properly, but not showing them properly at creation time.
Very strange.