Trying to use the Pro Main Menu Pack, Standalone preview gives me this error when I alt + tab. Also, looking at this link, is Epic aware of the issue and in the process of patching it?
Assertion failed: [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/Windows/D3D11RHI/Private/D3D11Util.cpp] [Line: 249] Result failed at D:/Build/++UE4/Sync/Engine/Source/Runtime/Windows/D3D11RHI/Private/D3D11Viewport.cpp:368 with error DXGI_ERROR_INVALID_CALL
UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_D3D11RHI
UE4Editor_D3D11RHI
UE4Editor_D3D11RHI
UE4Editor_RHI
UE4Editor_RHI
UE4Editor_RHI
UE4Editor_RHI
UE4Editor_SlateRHIRenderer
UE4Editor_SlateRHIRenderer
UE4Editor_Core
UE4Editor_Core
UE4Editor_RenderCore
UE4Editor_RenderCore
UE4Editor_Core
UE4Editor_Core
kernel32
ntdll