After upgrading from 4.15.3 to 4.16.3 I’ve got a crash when loading the map.
At first in FAsyncBuildInstanceBuffer::DoWork() Line 2587 ensure(InitializedIndexCount == NumRenderInstances) fires a debug break where InitializedIndexCount == 1 and NumRenderInstances == 2. PerInstanceSMData contains 1 Element and InstanceReorderTable contains 2 Elements.
When I ignore the ensure() a little bit later in UHierarchicalInstancedStaticMeshComponent::CreateSceneProxy() Line 2527 the check() fails with WriteOncePrebuiltInstanceBuffer.NumInstances() == 2 and GetNumRenderInstances() == 1
This crash happens in Debug, DebugGame and Development Builds and only in Packaged Builds. In Shipping it seems to work fine.
I’ve found some reports that doesn’t get an answer here and here.