It seems to be an issue with HDMI ingest if we look at the log file
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:230:FrontOfRoomPage_SizeChanged] Front of room page size changed
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:233:FrontOfRoomPage_SizeChanged] Front of room old size:1600,900, new size:800,450
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:111:RefreshFrontOfRoomScaling] Screen width in raw pixels (2736) is above threshold (1920). Resetting scaling to none (1.0).
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:118:RefreshFrontOfRoomScaling] Scaling transformation factor is set to 1
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:119:RefreshFrontOfRoomScaling] FrontOfRoomRootGrid's size is set to Width : 800 Height : 450
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:291:UpdateGalleryWindowSize] UpdateGalleryWindowSize: Gallery width changed to = 1600
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:292:UpdateGalleryWindowSize] UpdateGalleryWindowSize: Root grid actual width = 1600
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:92:FrontOfRoomPage_DpiChanged] DPI changed - Will setup Front of Room scaling.
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:122:RefreshFrontOfRoomScaling] Screen width in raw pixels (2736) is above threshold (1920). Resetting scaling to none (1.0).
08/14/2017 | 14:22:23 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:129:RefreshFrontOfRoomScaling] Scaling transformation factor is set to 1
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:130:RefreshFrontOfRoomScaling] FrontOfRoomRootGrid's size is set to Width : 800 Height : 450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:92:FrontOfRoomPage_DpiChanged] DPI changed - Will setup Front of Room scaling.
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:122:RefreshFrontOfRoomScaling] Screen width in raw pixels (2736) is above threshold (1920). Resetting scaling to none (1.0).
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:129:RefreshFrontOfRoomScaling] Scaling transformation factor is set to 1
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:130:RefreshFrontOfRoomScaling] FrontOfRoomRootGrid's size is set to Width : 800 Height : 450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:241:FrontOfRoomPage_SizeChanged] Front of room page size changed
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:244:FrontOfRoomPage_SizeChanged] Front of room old size:1600,900, new size:800,450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:243:FrontOfRoomPage_SizeChanged] Front of room page is now fullscreen
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:122:RefreshFrontOfRoomScaling] Screen width in raw pixels (2736) is above threshold (1920). Resetting scaling to none (1.0).
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:129:RefreshFrontOfRoomScaling] Scaling transformation factor is set to 1
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:130:RefreshFrontOfRoomScaling] FrontOfRoomRootGrid's size is set to Width : 800 Height : 450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:294:UpdateBackgroundImage] UpdateBackgroundImage: Root grid actual height = 450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:295:UpdateBackgroundImage] UpdateBackgroundImage: Root grid actual width = 800
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:81:FrontOfRoomPage_DpiChanged] DPI changed - Will setup Front of Room scaling.
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:111:RefreshFrontOfRoomScaling] Screen width in raw pixels (2736) is above threshold (1920). Resetting scaling to none (1.0).
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:118:RefreshFrontOfRoomScaling] Scaling transformation factor is set to 1
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:119:RefreshFrontOfRoomScaling] FrontOfRoomRootGrid's size is set to Width : 800 Height : 450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:81:FrontOfRoomPage_DpiChanged] DPI changed - Will setup Front of Room scaling.
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:111:RefreshFrontOfRoomScaling] Screen width in raw pixels (2736) is above threshold (1920). Resetting scaling to none (1.0).
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:118:RefreshFrontOfRoomScaling] Scaling transformation factor is set to 1
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualGallery.xaml.cs:119:RefreshFrontOfRoomScaling] FrontOfRoomRootGrid's size is set to Width : 800 Height : 450
08/14/2017 | 14:22:24 | 4640 | LVL_INFO :: [FrontOfRoomPageDualContent.xaml.cs:251:FrontOfRoomPage_SizeChanged] Front of room page is now fullscreen