Crash, The ordinal 1002 could not be located

Hi,

I’m building a post process material in 4.19, in a first person project for a cinematic.
It has just started crashing repeatedly upon launching.

There’s a post regarding this error report here, but it’s happening under quite different condtions for me.
It’s obvioulsy to do with the shader, any help would be appreciated.

Alex

Fatal error: [File:D:\Build++UE4+Release-4.19+Compile\Sync\Engine\Source\Runtime\RenderCore\Private\RenderingThread.cpp] [Line: 819]
Rendering thread exception:
Fatal error: [File:D:\Build++UE4+Release-4.19+Compile\Sync\Engine\Source\Runtime\Windows\D3D11RHI\Private\D3D11Util.cpp] [Line: 182]
Unreal Engine is exiting due to D3D device being lost. (Error: 0x887A0006 - ‘HUNG’)

0x00000000924AA388 KERNELBASE.dll!UnknownFunction ]
0x000000007B137884 UE4Editor-ApplicationCore.dll!UnknownFunction ]
0x000000003C1C6D9B UE4Editor-Core.dll!UnknownFunction ]
0x000000003C101949 UE4Editor-Core.dll!UnknownFunction ]
0x0000000024BCA0CF UE4Editor-D3D11RHI.dll!UnknownFunction ]
0x0000000024BCE5E0 UE4Editor-D3D11RHI.dll!UnknownFunction ]
0x0000000024BAD62A UE4Editor-D3D11RHI.dll!UnknownFunction ]
0x0000000024BAD58C UE4Editor-D3D11RHI.dll!UnknownFunction ]
0x0000000024BBAADF UE4Editor-D3D11RHI.dll!UnknownFunction ]
0x000000006371F0B6 UE4Editor-RHI.dll!UnknownFunction ]
0x0000000024991FF8 UE4Editor-SlateRHIRenderer.dll!UnknownFunction ]
0x0000000024997C4C UE4Editor-SlateRHIRenderer.dll!UnknownFunction ]
0x000000003BFDB713 UE4Editor-Core.dll!UnknownFunction ]
0x000000003BFDBD3A UE4Editor-Core.dll!UnknownFunction ]
0x000000007C883CC9 UE4Editor-RenderCore.dll!UnknownFunction ]
0x000000007C884CF6 UE4Editor-RenderCore.dll!UnknownFunction ]
0x000000003C3A9FFC UE4Editor-Core.dll!UnknownFunction ]
0x000000003C39ED63 UE4Editor-Core.dll!UnknownFunction ]
0x00000000950B3034 KERNEL32.DLL!UnknownFunction ]
0x0000000095691431 ntdll.dll!UnknownFunction ]
0x0000000095691431 ntdll.dll!UnknownFunction ]