Please make sure to update to the latest firmware version WW-16.0610.1911.89 (CPU:630)/ WW-16.0200.1907.501(CPU:430).
Could you let us know whether this battery drain issue is appearing when using the phone or in sleep mode?
If while using the phone, does battery drain while using any specific apps?
If there are battery drain issues in sleep mode, please follow the steps below and show us the screenshots.
1) Charge the phone to 100% before going to bed > remove the charger > Clear all apps in recent app list > turn off screen > the next morning before using the phone, please screenshot the two pages:
a) Settings > Battery
b) Settings > Battery > Advanced battery usage (tap the battery icon to access)
2) Tell me the battery variation: for example 23:00 (100%) > 08:00 (90%)
Thank you and have a nice day 🙂