Phone turns off when speaker plays audio/ No Signal/ No USB detection/ Battery Issue - Zenfone 5

Hi,

I use ASUS Zenfone 5 (A501CG); Firmware : 3.24.40.78; Android 5.0.

I'd like start by pointing out that my Zenfone began to dysfunction sequentially(part by part) over a period of time. All the problems did not occur at the same time.

- Currently, both the SIM slots are not working.
- USB rarely detects the phone.
- Phone turns off when ever an audio is played.
- Battery is discharging very fast.

Few weeks before the phone broke down, i noticed that the LED indicator wouldn't go off even after i'd plug out the charger. I felt its an update issue or something.

One day I set an Alarm for 7 A.M. That morning at 7 A.M the phone made a loud beep and it switched off. It followed the entire day(until now). Whenever i'd get a call the phone would switch off. Even a message beep would turn the phone off. So i kept the phone in silent mode. Any audio from the speaker would result in the phone switching off. However audio over earphones had no problem.

Later that evening SIM card slot 1 stopped working. SIM slot 2 was working fine.

Next day i tried connecting my phone with the PC via USB , but it wouldn't detect the phone. I tried updating the PC drivers and what not but nothing helped. Following evening SIM card slot 2 stopped working as well. After lot of hard work somehow the phone was detected. Not very often, but sometimes the PC detects the phone.

Phone takes lot of time charging, and discharges quickly.

Please note : All the problems occurred one after the other as i mentioned (sequentially).

Could you please tell me what could be the core problem? Is it the chip set?
I'll visit the service center, but i'd like to know what could possibly be wrong before i hand them the phone.