What can be the reason that an iPhone SE 3rd gen. loses battery power significantly over night when it is completely shut down? The flight mode was activated before the shutdown. The device is brand new, battery capacity and health is on 100%, no background tasks are allowed. It is a replacement for the same model, which had the exact problem some weeks ago.
If it is completely shut down there should no third-party app do anything. Even when I switch off the Bluetooth beacon which helps to locate the phone when it is shut down there is this massive power loss.
I found similar reports on the internet, also from Android users. Most of them assume a failing capacitor on the main board. If this would be the case then it would happen the second time at a brand new iPhone.