This may be present on other platforms, but the immediate case is on android.
given:

    videoRecorder {
	audioCodec: "aac"
	mediaContainer: "mp4"
	frameRate: 30
	videoEncodingMode: CameraRecorder.AverageBitRateEncoding
	resolution: Qt.size(1920,1080)
	videoCodec: "h264"
    }

is not enough to produce a recording matching the specified properties.

I had to add:

onRecorderStateChanged:  {
	camera.videoRecorder.resolution =  Qt.size(1920,1080);
}

to get it to actually take and remain. It seems that somewhere along the line the preference is getting lost. I'm guessing it's when it goes into unloaded state and comes back out?

D libacquirefaces.so: qrc:/main.qml:98 (onRecorderStatusChanged): qml: recorderStatus: LoadedStatus
D libacquirefaces.so: qrc:/main.qml:109 (onRecorderStateChanged): qml: recorderState: undefined
D libacquirefaces.so: qrc:/main.qml:98 (onRecorderStatusChanged): qml: recorderStatus: UnloadedStatus
D libacquirefaces.so: qrc:/main.qml:98 (onRecorderStatusChanged): qml: recorderStatus: LoadedStatus