Battery problem

My phone got weird battery problem

My phone is 2 yr old & battery replaced last yr
S Off using custom rom insertcoin senseven artmod
I think physically battery is ok

Problem is phone shows battery discharging very quickly
after that what I do
reset battery stats by power off or auto shut down by low battery then holding vol up & power button screen on till phone off again then start phone again it will shows increased battery %
For eg using phone for 10 hrs with 1 hr screen on time it discharge 100 to 0% then I reset battery stats & start phone again it will shows 65% battery

2 nd thing if I'm charging phone it wether phone on or off (let's assume 35% ) it's % not increased but it shows phone using more power after some time it will shows less battery (15%)but in reality phone is charging after resetting battery stats with above method it will shows correct %(55%)

I tried these methods to correct it
Flash stock firmware again unsuccessful
Flash stock ruu again unsuccessful

What I should do ?

I count manually battery life it's above 24 hr with screen on time of 2.5 hr