I'm not sure yet how to verify that but I think that since the ESP32 is getting hot, it's maybe the regulator of the USB that was defect and delivered 5v in place of 3.3 V that the ESP32 need.
Also, for the design of the M5STICK, ESP32 and the battery are in contact, it doesn't help.
Can be dangerous if ESP32 is hot due to high cpu usage ?

Yep :) I have asked for a refund/replacment.
I'm curious if anyone else had the problem.

Hello everybody, I have just received my M5STICK, the grey one with the Watch belt.
I have connected the unit to my PC using the usb c cable to connect to my computer to start to play with it.
But the unit has taken fire.
The Inside battery is unusable and has inflated. The lcd screen is damaged due to the heat.
Unit can be powered on when connected to usb port without the battery, but the ESP32 is getting dangerously hot.
Not sure if it's the battery or or the ESP32 the problem.
So, is other poeple had expercienced the same kind of problems ?