Selfie and non-selfie photos taken by the Camera App get distorted?

Hi folks,

When I tried to take some portrait photos (either selfies or non-selfies), my face looked normal and symmetrical on the viewing screen. But when I hit the shoot button, my face would look completely distorted and very asymmetrical in the resulting photos.

I have double-checked with another phone (a non-iOs one), and my face looked normal like exactly what I would see in a mirror.

This problem is also occurring to my other iPhone 6S plus as well. I have attempted to reset both devices and tried to find if there are any ways to reset the settings for the Camera but did not seem to work :(

Many thanks if you can help me fix this problem : )