This is not a bug. It happens when app targets 10.0.14393.0 SDK but is ran on Windows 10586 OS with WACK (version 10.0.14393.0)

We should update FAQ with this info.

To reproduce:
1. Build empty project for UWP
2. Open solution
3. Click on Project -> Store -> Create App Packages -> yes -> ... -> choose "Master" for the Solution Configuration and let the "Include full PDB symbol files...." checked. -> Create
4. Let the Windows App Certification Kit to validate the package
5. See the failed result

Reproducible: 5.5.0a6, 5.4.0p2, 5.3.6p3, 5.2.5f1

Why Won't Fix: This is a Microsoft bug, nothing we can do on our side.