AR Vuforia integration - Strange behavior of recognition

Hello,

I have setup a sample recognition project:

Unity 5.4.0f3 x64 and vuforia-unity-6-0-117

https://www.dropbox.com/s/pesaqjkx1qm2t3o/vuforia_problem.mp4?dl=0

as you can see in the movie, strange things happen, and it recognizes and stops (hangs) randomly,

sometimes it recognizes few times in a row and after it hangs you must wait or turn it few times,

it does not depend that i cleared console, it just happend to unfreeze after this in the movie but it is not a rule.

Strange thing is when it freezes it still recognizes as you can see when I enable mesh of a child target

It happens the same in Editor, Android build on real devices and in PC build

maybe someone knows it and can help, before i will go thru the code, coz i just start with Vuforia, and if that bug shows with the sample and with default setup it is not very encouraging to use Vuforia, coz ARtoolkit has also bugs and had to search for myself, so why to pay for bugs in Vuforia

All the best,

Paul