You should never update a system app (other than Gapps) on our ROMs. You will lose all of the patches we've applied on the specific MIUI app to enable its features. There is no system app updater and it is not possible to have one, as we don't alter the original signature of the apps.
As for the camera issue, found the issue and solved it. This is an official Android 9 bug that can only be encountered in certain situations and only on certain devices. Google already fixed that issue on Android 10, but it still plagues Android 9. I'll include the fix in next release.