Inconsistent frame rates

I'm seeing inconsistent rendering frame rates on the HoloLens, even with a graphically very simple scene.
The quality setting is set to "Fastest", and in approximately 50% of application runs I get smooth 60fps rendering.
However, in the other cases I either get 30fps or it is fluctuating between 30 and 50fps. In these cases I see significant jitter on the holograms. I guess this is a result of predictive tracking not working properly at lower frame rates. I even see this with one and the same app behaving differently just by pausing it with a bloom gesture and resuming it by tapping the app panel again.

I tried the profiler to find out what could cause this, but all it tells me is that "HoloLensWaitForGPU" is sometimes taking 7-10ms, and sometimes way more (23-27ms). Switching to "Deep Profile" does not reveal more information.

The app that I'm running is also using Vuforia to detect and track targets, but according to the profiler non of the scripts are spending a considerable amount of time, please see screenshots attached.

Any ideas what could cause this or what I could look at to debug this further?

 

What this indicates is you have working happening on the GPU. In the case where you waited 26 ms this is because you missed a v-sync so an entire frame had to be skipped. I would recommend adding the GPU profiler to see what is taking so long on the GPU. Additionally you can try using Visual Studios graphics profiler