my 6p battery drained drastically recently, sometimes it drained all battery after a night even after fully charge before sleep.

i didn't update it to nougat and using stock OS. i check the cause of battery drain was from Cellular Network Signal, i quick google and found this is a bug from android which cause the phone keep looking for cellular network, the problem still persist even after update to nougat

does anyone know how to resolve this issue other than replacing the battery?