I bought a Xiaomi Mi Box S and it's intermittently dropping the Wi-Fi connection. When it does work I get 4 bars. I'm streaming video from SMB on LAN with Kodi and sometimes it works fine for a long time but then it starts buffering or completely stopping playback because the network is disconnected. It also happens with other apps, and sometimes the Wi-Fi network state is randomly changed to "Disabled" or it says the saved password is incorrect. This happens with both 2.4 GHz and 5 GHz.
My box did the same thing. Ended up buying a cheap usb to ethernet adapter and haven't had any issues since.