Thanks for your answer, i forget to give you some more detals the project is for Android (the current test device is Galaxy S7, Android 8, The Unity version is tle last 2018.3.2, and Vuforia 8.
I move back to Vuforia 7.5 and the problema dissapear, let me try to explain you a Little more
The Project start in AR and user can switch to VR for a video 360 (when click on imagetarget or VU Mark), with Vuforia 7.5 all run smooth I just use MixedRealityController for switching modes, with Vuforia 8 switching to VR the Positional tracking still running (i see on logcat the tracker status).
I try to stop the positional tracker and enable the rotational tracker in both way, with Vuforia configuration inside Unity IDE and with code but the camera stop rotating, so I dont know whats the properly way to do, maybe the code need to implement with events and wait until positional tracker stops to start the rotational? Please if you have some code i will apreciate.
Anyway is working different with Vuforia 7.5 and 8, so could be a bug?
Why not implement 2 more modes for VR in MixedRealityController, one with Rotational only and another with Rotational Positinoal so we can take advantage too if want to be on VR with positinoal tracking with Ground plane.
Thanks in advance