As I have 5 Ceiling Lights and I started monitoring of their activity. 4 of them connected to one wifi router and one to another. I found very interesting thing. It seems that disconnection from wifi is not a bug, but a feature of the devices as I see from the log, that they dropping connections with wifi at the exact same time, even been connected to different routers. Also other devices in the network (IoT, laptops, cellphones, etc) does not have same issues at that moment.
Positive observation is that in most cases ceiling light reconnects to wifi less then in a minute, but some times failed.
Today log:
2020.06.23 4:46:06 YLXD02YL, Light state: unavaliable
2020.06.23 4:46:06 YLXD17YL, Light state: unavaliable
2020.06.23 6:10:24 YLXD16YL_mish, Light state: unavaliable
2020.06.23 6:20:39 YLXD17YL, Light state: unavaliable
2020.06.23 6:52:10 YLXD05YL, Light state: unavaliable
2020.06.23 6:52:10 YLXD17YL, Light state: unavaliable
2020.06.23 7:03:32 YLXD16YL_andr, Light state: unavaliable
2020.06.23 7:23:41 YLXD05YL, Light state: unavaliable
2020.06.23 7:35:03 YLXD16YL_andr, Light state: unavaliable
2020.06.23 7:35:03 YLXD05YL, Light state: unavaliable
2020.06.23 7:35:03 YLXD16YL_mish, Light state: unavaliable
2020.06.23 7:35:03 YLXD02YL, Light state: unavaliable
2020.06.23 7:35:03 YLXD17YL, Light state: unavaliable
2020.06.23 7:55:12 YLXD16YL_mish, Light state: unavaliable
2020.06.23 8:08:36 YLXD16YL_andr, Light state: unavaliable
2020.06.23 8:08:36 YLXD05YL, Light state: unavaliable
2020.06.23 8:08:36 YLXD17YL, Light state: unavaliable
2020.06.23 8:16:57 YLXD02YL, Light state: unavaliable
2020.06.23 8:28:45 YLXD16YL_mish, Light state: unavaliable
2020.06.23 9:00:16 YLXD16YL_mish, Light state: unavaliable
2020.06.23 9:15:46 YLXD16YL_mish, Light state: unavaliable
2020.06.23 9:43:09 YLXD16YL_andr, Light state: unavaliable
2020.06.23 9:43:09 YLXD05YL, Light state: unavaliable
Model numbers of my lights:
450-YLXD16YL
450-YLXD16YL
480-YLXD17YL
480-YLXD05YL
650-YLXD02YL