Hello. @ka_wai.yuen and welcome to the community 
, I’m sorry you’re facing this. A frozen face with a moving body is a classic sign of a firmware cache issue. The Debug App temporarily clears this cache, which is why it worked for a while.
The permanent solution is to re-flash the firmware. You must contact Living.AI support
( service@living.ai ) and ask for the official resource package and instructions for your EMO model. This will completely reset the software.
In the meantime, try a hardware restart using the physical reset hole on EMO’s head. It’s a stronger reset than just turning it off.
I hope this helps! Good luck!
Hamza