@isaacmehler @jayeff Just a small update. I got the multimeter and checked everything. There's no potential difference between the cable and the ports. It just turns out all the metal shields are grounded. And there's no power leakage from the adaptor. The adaptor normally provides 20V and after it "stops" working, it outputs 2V. And me being a noob somehow screwed up and caused a small spark when measuring Amps. But something weird happened after this. The issue was gone temporarily. The laptop ran fine for a while. Even though the issue is back, it only happens when the laptop is under heavy load.
Now, I believe it's just the power adaptor gone bad. I'll get it checked and replace if needed. Thanks for the help and Happy New Year!!