Error during custom RayTracer Shader initialization

Development Rendering
2

Ok some more info here:
these init buffers are filled in

FRayTracingScene::Create

by a separate thread

// Fill instance upload buffer on separate thread since results are only needed in RHI thread
GraphBuilder.AddCommandListSetupTask(...)
{
...
FillRayTracingInstanceUploadBuffer(
				RayTracingSceneRHI,
				PreViewTranslation,
				Instances,
				InstanceGeometryIndices,
				BaseUploadBufferOffsets,
				BaseInstancePrefixSum,
				NumNativeGPUSceneInstances,
				NumNativeCPUInstances,
				MakeArrayView(InstanceUploadData, NumNativeInstances),
				MakeArrayView(TransformUploadData, NumNativeCPUInstances * 3));
...
}

so it looks like a sync issue… My plugin is marked as PostConfigInit and the shader is iexecuted during postOpaqueRender step, so I am wondering how to sync it properly