TAB S 8.4" Very Very Weird Problem need help

So my TAB S is a few months old like 3 months now

I only installed few top rated APPS and everything is working fine, i use it to facebook and youtube and reading and some emails, i rarely game on it

2 days ago something very weird started to happen when battery reached 30% the device slowed down and froze up and rebooted on it's own, when it boots up , it forgets the wifi password, and the battery is like 15%

freezes up again after 30 seconds of using , and again reboots, forgets wifi password, battery level is 10% , a minute later same thing battery like 4% HOWEVER

IF I TURN IT OFF ,AND PLUGGED IN THE CHARGER IT SAYS 29% AND CHARGING.... so the battery level from within the OS is not true and it freezes and reboots and upon that forgets the password of the wifi

I DID NOT ROOT IT , I TAKE VERY GOOD CARE OF IT

now i tried draining the battery all the to 1% and 0% then full charge , and it wroks untill it reaches 30% - 25% then problem all over

if i plug it in the charger and use it , it seems fine

what could be the problem and do i have to factory reset?

from xda-developers http://ift.tt/1B1p9MT

via IFTTT