To fix the issue, please do the following.
1. Click on Settings
2. Select Apps & Notifications
3. Select the Camera app
4. Select Storage
5. Select Clear Cache
6. Select Clear Data
Now restart the camera app and you'll notice that when you take a photo, it doesn't say 'Processing'.
This is the only way to fix the situation at this time, so if / when you next see 'Processing', just follow these easy steps and the camera app will work as normal once more.