Just got my phone on Tuesday. It was working fine, battery life was amazing. Yesterday night, i charged it to 95% and went to sleep (i turned off wifi and LTE). I woke up in the morning and my phone wasn't even turning on with the power button. I had to hold volume down and power button together for 7 seconds. Once it turned on, i went to the battery usage graph and it shows that the battery went from 95 to 40 instantaneously (literally a vertical line drop). I charged it up again and it is working fine now but who knows what'll happen when I go to sleep tonight.
Can anyone explain what caused this problem? I've never seen something like this and could not find a solution.