CMMotionManager Device Motion Wobbles under iOS 14

I have an old iOS app that doesn't use GoogleVR, instead it rolls it's own VR framework, but once I upgraded to iOS 14 the data coming from CMMotionManager is very wobbly, or shaky, even if I place the phone flat on a table. Am I doing something wrong or do I need to use a different way to access the data? I've seen the Official Google VR team state they had to fix a similar issue, but I'm unable to find their changes, since it is buried inside compiled code for their Unity Plugin.

The code in question is at: https://github.com/mgatelabs/SCN-VR/blob/master/scn-vr/CoreMotionTracker.m

But the main parts would be as follows

But i'm starting the process with:

Code Block language
[self.motionManager startDeviceMotionUpdatesUsingReferenceFrame: CMAttitudeReferenceFrameXArbitraryZVertical];

And then i'm reading and transforming the data like this:

Code Block language
CMQuaternion currentAttitude_noQ = self.motionManager.deviceMotion.attitude.quaternion;
GLKQuaternion baseRotation = GLKQuaternionMake(currentAttitude_noQ.x, currentAttitude_noQ.y, currentAttitude_noQ.z, currentAttitude_noQ.w);
GLKQuaternion rotationFix = GLKQuaternionMakeWithAngleAndAxis(-M_PI_2, 0, 0, 1);
if (self.landscape) {
    self.orientation = GLKQuaternionMultiply(baseRotation, rotationFix);
  } else {
    self.orientation = GLKQuaternionMultiply(rotationFix, baseRotation);
  }

And it is all wobbly, which isn't that great for VR.