Vertex Interpolators broken in landscape materials

D:/Unreal/UE4_Release-4.27/Engine/Shaders/Private/LandscapeVertexFactory.ush(788,3-59): Shader FDebugViewModeVS, Permutation 0, VF FLandscapeVertexFactory[Image Removed]:/Unreal/UE4_Release-4.27/Engine/Shaders/Private/LandscapeVertexFactory.ush(788,3-59): Shader FDebugViewModeVS, Permutation 0, VF FLandscapeVertexFactory:

error X3017: 'GetMaterialCustomizedUVs': cannot implicitly convert from 'float2[4]' to 'float2[5]'

[2021.08.17-10.39.36:950][772]LogShaderCompilers: Warning: Failed to compile Material /Game/ThirdPersonCPP/NewMaterial.NewMaterial (MI:/Game/ThirdPersonCPP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.Landscape_0.LandscapeMaterialInstanceConstant_0) for platform PCD3D_SM5, Default Material will be used in game.[

1. Create a new project or open an existing level.
2. Create a new material
3. Add the licensee expression code from here -
   1. [Link Removed] 
   2. (Alternatively just plug any value into a VS interpolator node)
4. Plug the VS node into the base pass and/or emissive + save the material.
5. Create a new landscape with the new material.
6. May need to rebuild the scene/lighting

On 4.26 - The material is black rather than white

On 4.27 - There is a landscape vs shader compilation error (see description).