SwapChain ResizeBuffer invalid

I have an UnrealEngine v4.9.0 application that I'm running Graphics Monitor 2015 R3.  Initially everything works fine - I'm able to run without issue.  But if I toggle on hmd (stereo) mode, I get the following...

Fatal error: [File:D:\PERFORCE_WORKSPACE\NU_REALITY\UNREAL_ENGINE\Engine\Source\Runtime\Windows\D3D11RHI\Private\D3D11Util.cpp] [Line: 200]
SwapChain->ResizeBuffers(1,SizeX,SizeY,GetRenderTargetFormat(PixelFormat),DXGI_SWAP_CHAIN_FLAG_ALLOW_MODE_SWITCH) failed
 at D:\PERFORCE_WORKSPACE\NU_REALITY\UNREAL_ENGINE\Engine\Source\Runtime\Windows\D3D11RHI\Private\D3D11Viewport.cpp:213
 with error DXGI_ERROR_INVALID_CALL

If I'm not running Graphics Monitor, I do not get the crash.  Please advise.

Thanks,

Jason