1. What happened

Exception thrown at 0x00007FFD9A7EA839 (KernelBase.dll) in 17.4toggle.exe: WinRT originate error - 0x8000000E : 'An attempt was made to acquire a buffer before it became available. Present() must be called before attempting to acquire this buffer.'.
analog\input\mirage\publicapi\compositionlayerd3d11bufferpool.cpp(204)\Windows.Mirage.dll!00007FFD6BDD000F: (caller: 00007FFD6BD734B5) ReturnHr(2071) tid(2f34) 8000000E A method was called at an unexpected time.
analog\input\mirage\publicapi\holographiccamerarenderingparameters.cpp(262)\Windows.Mirage.dll!00007FFD6BD734D3: (caller: 00007FFD6BD662C7) ReturnHr(2072) tid(2f34) 8000000E A method was called at an unexpected time.
onecoreuap\windows\wgi\winrt\display\displaycommon.cpp(411)\Windows.Graphics.dll!00007FFD783804B0: (caller: 00007FFD7838017A) ReturnHr(9) tid(3ecc) 80070490 Element not found.
analog\input\mirage\publicapi\holographicframe.cpp(352)\Windows.Mirage.dll!00007FFD6BD661B4: (caller: 00007FFCFB844920) ReturnHr(2073) tid(2f34) 8000000E A method was called at an unexpected time.
Failed to update back buffer on holographic camera - renders may become out of sync! Error code: '0x8000000e'

2. How we can reproduce it using the example you attached

- using attached repro project, deploy to WMR HMD and use Q button to toggle XR. When XR is enabled after being off, the mirage failure occurs.