First just clear the cache of camera app and see if the issue is fixed. Still facing the issue ?Try to see if it works properly in safe mode.
Steps to enter Safe mode when power is on:
1. Long press power key.
2. Tap and hold “Power Off”.
3. Tap " OK " of Reboot to Safe Mode window.
4. " Safe mode " reminder appears on the lower-left of home screen.
How to Exit Safe Mode ?
Restarting your device. Your device will now be exit safe mode.
NOTE：If the system can not exit safe mode, please try to unplug and reinstall battery again ( IF the battery is removable). Meanwhile, please check if the volume key is stuck or faulty.
How to Enter and Exit Safe Mode on Android phone ? | Official Support | ASUS India
