Did you go through the dimming configuration? Flickering usually happens when the dimmer circuit isn't passing enough voltage to the bulb. Once you set the lower limit, the switch will set the buttons' dim range from there to max.

1. Go into the app and open up the screen for a dimmer.
2. Tap the gear icon in the upper right.
3. Tap on Dimming Calibration near the bottom
4. Slowly tap the dimming icon until the light starts to flicker.
5. Tap the brighten icon once, check that the flicker has stopped -- repeat slowly, checking each time until the flickering stops.
6. Once the flickering has stopped, that's your lower voltage limit. Set it and forget it.

I did do calibration of dimmer quite a few times. Sometimes it works fine but other times its flickers. It's kind of unpredictable. But it does flicker eventually.