Me and my cousin both have the same problem. I had about 70% charge at night, when I woke up in the next morning it reached about 50%. The same thing happened the next day too and also my battery gets low on 6 hrs of usage.
same issue happened in my Nokia 7 Plus device also..
even if the mobile is an ideal conditions it use drain the battery lot... around per hrs .its drain almost 7% off battery
so plz fix this issue in October OTA security patch
before android p update .. 100 to 50% of charge it last upto 4hrs 20min.... but now for the 4hrs of screen on time it's took 100 to 39% of charge.... plzzz do optimise the battery for the battery performance