Android System draining battery, tried many fixes, pls help

[Lure852]

I have had this S7 since last Christmas with no issues with battery life. Basically the "Android System" is slamming my battery hard and draining it from full to zero in just 2-3 hours with absolutely nothing being used on the phone, in airplane mode with location and data off.

I have recently moved from the US to the UK, so I am not sure if that has something to do with what is going on, but as I said, I have tried disabling as much as possible with no appreciable change.

Things I have tried:
Clearing cache partition
power save mode
power save with location turned off
power save in airplane mode with location turned off
checking apps for activity, barely anything is on

See screenshots, the issue has gotten progressively worse. Initially it was just a very high percentage, but now my phone isn't even charging up. On the screenshot with 69% Android usage, it was on the charger (fast charger) all night, but couldn't even charge to full.

After that happened, I turned it off to charge it to full but when I turned the phone on, it had done that "reset" where the screen is all zoomed in and a ton of my system settings had been reset but all my apps and data were still in place. I fixed the screen resolution by disabling high performance mode, and the battery drain continues...

Please advise, thank you.

 

[B. Diddy]

Welcome to Android Central! What's your cell signal like? The one screenshot with the signal indicator shows only one bar. Install GSam Battery Monitor and look at the cell signal graph over the span of a battery charge. If it's persistently poor, that can kill the battery (although I'd expect Cell Standby to be high on the battery list in that case).

 

[Lure852]

The cell signal is pretty bad here, 1 or 2 bars usually. Thing is, I had the phone on airplane mode for a lot of the time, including the overnight represented by that second screenshot.

It didn't repeat that performance last night at least, but battery is still being drained fast. Right now my phone is projecting 3 hours battery life based on usage since it came off the charger. Android system is still slamming my phone hard.

 

[B. Diddy]

If you tap Android System, does it give you a more detailed breakdown of what components are active?

 

[Lure852]

I mean yeah, about 50 different things; everything from Knox, to help, to bootagent, to themes, to smartfaceservice.... everything.

Ultimately after a lot of research and waiting around on this forum for advice, I decided to back up my phone and do a factory reset. The problem seems to have gone away, so hurray for BS solutions to problems no one seems able to even put their finger on.