I don’t get any errors when I build my app in Unity, nor do I get any errors when building from the Visual Studio solution. When I launch it on the HoloLens I get a splash screen, then after a few seconds I get an exception accompanied by this stacktrace:
For what it’s worth, I get the same exception when I try to launch it on my local machine in Visual Studio, so it seems like this is a UWP issue. I tried building to a clean folder and I tried deleting my Unity library folder, but the exception still shows up. The exception goes away when I roll back to Unity 5.5.2 and it was not present as of Unity 5.6.0f1b because I used that version to build several demos of my project last week. I’m not sure what to do at this point because it looks like the exception is coming from internal Unity code.
In you Unity project folder can you try deleting everything in there expect the Assets and project settings folder, make a backup just in case. Can you let us know the result?
If the issue is still happening can you submit a bug report with a min repro project?