Bluetooth and WiFi problem

You mean those sliders do not stay ON? Or that you can not find any network or bluetooth devices nearby?

Did you try the hard reset:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side button. When the Apple logo appears, release the button.

How do you mean - what kind of error or malfunction do you see with those features?

I updated to 14.4.2 last night and havent seen any problems yet. This is an iphone8 though.