Smart view is not working properly,only audio is audible after connecting ,screen mirroring,Videos are not displaying,my smart tv is Toshiba , Earlier there was not such problems.but my another phone realme is connected well,i  think this is problem ...

After updating to one Ui 3.0 my m 21 is having battery drain issue while in sleep mode .it grains from 6 to 7 percent within 7 hours ,even when data is off,before update it there was no issue ,kinly advise .