I created a simple scene with a Vuforia image target, consisting of a cube attached to the Mars Astronaut image. The cube is horizontally displaced from the target, so that I can test if the cube is still displayed if the target is not in the field of view of the camera. I have enabled extended tracking by checking "Track Device Pose" in the Vuforia Configuration. I am using Unity version 2019.2.6f1 and Vuforia version 8.3.8. When I run the app in the Unity Editor (with an attached webcam), extended tracking works fine, and I can still see the cube when the target is not in the field of view of the camera. However, when I deploy this to my Android Pixel 3 phone, extended tracking does not work - the cube immediately disappears when the target is not in view. I have put core-1.4.0.aar in the Plugins/Android folder as per the Vuforia instructions. (I have also tried later versions or core-xxx.aar, with the same problem). If I use an older version of Unity (2018.3.10.f1) and Vuforia (8.1.10), then extended tracking works fine (on the same scene, and on the same Pixel 3 phone). Any ideas?