I am using Unity version 2017.3.1f1 and Vuforia 7.1.31
I created a bare-bones Unity app for the hololens that launches a cube from a basic image target. It recognizes the image right away and the cube appears immediately--no problems there.
I specified "Extended Tracking" to be on in the Image Target Behavior script, and it is. I can move the target away and the cube stays. It appears to be rock steady as long as I am about 0.5 meters away from it, rock steady. But when I get further away, it tends to jump and blur, very sensitive to my head motion. When I stand perfectly still, it settles down. Looks like it's position is slow to update, unlike basic holograms created without vuforia.
So, something is going wrong with the handoff from Vuforia to the Hololens' native tracking described in https://library.vuforia.com/articles/Training/Developing-Vuforia-Apps-for-HoloLens
I get the same behavior from a full build-out of the "Vuforia Hololens Sample" at https://assetstore.unity.com/packages/templates/packs/vuforia-hololens-sample-101553
It appears that I will need to manually set an anchor for the created object and explicitly turn off Vuforia, as described in the Jan 16th post on this thread: https://developer.vuforia.com/forum/hololens/using-world-anchors-vuforia-extended-tracking
Please let me know if there is a faster way. Some setting, perhaps?