Why is Dynamic Material Instance not working :(?

Applying the same material used in the named material override to the base mesh. Repeatably too.

MachineId:246DC646418D4295A55CE8A05E9F88BE
EpicAccountId:23fde36909b6437fb8020a7b9013da03

Access violation - code c0000005 (first/second chance not available)

UE4Editor_ShaderCore!FVertexFactory::Set() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\shadercore\private\vertexfactory.cpp:180]
UE4Editor_Renderer!TBasePassDrawingPolicy<FUniformLightMapPolicy>::SetSharedState() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\basepassrendering.h:819]
UE4Editor_Renderer!FDrawBasePassDynamicMeshAction::Process<FUniformLightMapPolicy>() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\basepassrendering.cpp:433]
UE4Editor_Renderer!ProcessBasePassMesh<FDrawBasePassDynamicMeshAction>() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\basepassrendering.h:1267]
UE4Editor_Renderer!FBasePassOpaqueDrawingPolicyFactory::DrawDynamicMesh() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\basepassrendering.cpp:509]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::RenderBasePassDynamicData() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:419]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::RenderBasePass() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:2022]
UE4Editor_Renderer!FDeferredShadingSceneRenderer::Render() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\deferredshadingrenderer.cpp:1137]
UE4Editor_Renderer!RenderViewFamily_RenderThread() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\renderer\private\scenerendering.cpp:1931]
UE4Editor_Renderer!TGraphTask<FRendererModule::BeginRenderingViewFamily'::25’::EURCMacro_FDrawSceneCommand>::ExecuteTask() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\core\public\async askgraphinterfaces.h:999]
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\core\private\async askgraph.cpp:932]
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilQuit() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\core\private\async askgraph.cpp:679]
UE4Editor_RenderCore!RenderingThreadMain() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\rendercore\private\renderingthread.cpp:319]
UE4Editor_RenderCore!FRenderingThread::Run() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\rendercore\private\renderingthread.cpp:440]
UE4Editor_Core!FRunnableThreadWin::Run() [d:\build++ue4+release-4.12+compile\sync\engine\source\runtime\core\private\windows\windowsrunnablethread.cpp:74]