I have an Ikea trådfri bulb connected to my Webthing gateway using the conbee II usb stick. I can set the dimming and switch the light on and off. However…
Situation 1
On the Webthing homescreen I have the light as a Light Thing. When I press the “button” on the homescreen the bulb turns On but the “button” on the screen is still in the off mode 
When I go into the thing (click the small web button in the top right of the light button) the situation is correct.
When I then go back to the mainscreen the button is shown as On again.
Situation 2
The light is On and on the homescreen it is show as On. I press the button and the bulb turns off and the button shows the light as Off. If I then refresh the page (F5) the light will be shown as On again, while the actual light is off. When I then go into the Thing the slider will be at On, the bulb in the middle will also be at On. Clicking the bulb in the middle or clicking the on/off slider will set both back to the Off mode (bulb stays off)