Having that problem from the beginning. When battery is on the 10% level then it rapidly goes down and having 5% smartphone is off. Factory reset did not help, as well as using smartphone in safe mode ( when only default apps are available)

Ps I had the same problem with my previous S8...however my wife who is still using her S8, can normally use phone for like 1 hour being on 10% level of battery...

I have just bad luck with batteries ???