Frequent disconnection on Yeelight LED Smart Bulb M2

I have replaced my room with Yeelight LED Smart Bulb M2 Color, total 5 of them. All of them are powered by 3 switch (2,2,1 for each power switch) and connect via Google Nest. I have done setting up them, and they are able to react to voice command on google nest and google home application.

The problem lies when some of the light bulb randomly(yes, the lightbulb that is not responding is different each time) stop responding to voice command and app for every overnight. I usually off then on back the power switch hopefully get it work ( its take several times) and sometime I resort to reset the lightbulb and set it again ( sometime it take awhile too , the app will doesn’t not detect the bulb for the first few times reset).

May I know whether someone encountered this before or could guide me on how to troubleshooting them?