Editor crashes while sculpting landscape heavily covered in foliage

Sculpting a landscape densely covered in foliage crashes editor after freezing.

Frequency: 2/2

crashreporter: N/A

Additional CrashReporter - [Link Removed]

Repro steps:

1. Open Editor (any project)
2. Open Modes>Landscape>fill world>Create
3. Open Modes>Foliage
4. Add asset to foliage type
5. Set brush size to 50,000 units
6. Paint foliage onto landscape (specific amount unknown ) until framerate drops to a noticable level
7. Switch to landscape sculpt mode
8. Set brush size to 50,000
9. Begin sculpting landscape

Results:

Editor crashes after freezing

Expected:

landscape is sculpted, foliage moves with landscape alterations.

MachineId:4E82586D46B558EA69EF0EAA821297B1
EpicAccountId:2e342bbd0e92480fa71bf4505b6a81c3

Assertion failed: (Index >= 0) & (Index < ArrayNum) [Link Removed] [Line: 785]
Array index out of bounds: -212592 from an array of size 124216

UE4Editor_Core!FDebug::AssertFailed() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\core\private\misc\outputdevice.cpp:430]
UE4Editor_Engine!UHierarchicalInstancedStaticMeshComponent::UpdateInstanceTransform() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\engine\private\hierarchicalinstancedstaticmesh.cpp:1925]
UE4Editor_Landscape!ULandscapeHeightfieldCollisionComponent::SnapFoliageInstances() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\landscape\private\landscapecollision.cpp:1190]
UE4Editor_LandscapeEditor!FHeightmapAccessor<1>::SetData() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\landscapeeditor\private\landscapeedmodetools.h:666]
UE4Editor_LandscapeEditor!FLandscapeToolStrokeSculpt::Apply() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\landscapeeditor\private\landscapeedmodepainttools.cpp:482]
UE4Editor_LandscapeEditor!FLandscapeToolBase<FLandscapeToolStrokeSculpt>::BeginTool() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\landscapeeditor\private\landscapeedmodetools.h:1324]
UE4Editor_LandscapeEditor!FEdModeLandscape::InputKey() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\landscapeeditor\private\landscapeedmode.cpp:1245]
UE4Editor_UnrealEd!FEditorModeTools::InputKey() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\unrealed\private\editormodemanager.cpp:640]
UE4Editor_UnrealEd!FEditorViewportClient::InputKey() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\unrealed\private\editorviewportclient.cpp:2068]
UE4Editor_UnrealEd!FLevelEditorViewportClient::InputKey() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\editor\unrealed\private\leveleditorviewport.cpp:2494]
UE4Editor_Engine!FSceneViewport::OnMouseButtonDown() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\engine\private\slate\sceneviewport.cpp:390]
UE4Editor_Slate!SViewport::OnMouseButtonDown() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\slate\private\widgets\sviewport.cpp:182]
UE4Editor_Slate!<lambda_7097b900f0e4be30d80fb18f98c51ea0>::operator()() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4459]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_7097b900f0e4be30d80fb18f98c51ea0> >() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:214]
UE4Editor_Slate!FSlateApplication::RoutePointerDownEvent() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4448]
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonDownEvent() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4406]
UE4Editor_Slate!FSlateApplication::OnMouseDown() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:4340]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\core\private\windows\windowsapplication.cpp:1353]
UE4Editor_Core!FWindowsApplication::DeferMessage() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\core\private\windows\windowsapplication.cpp:1732]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\core\private\windows\windowsapplication.cpp:697]
UE4Editor_Core!FWindowsApplication::AppWndProc() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\core\private\windows\windowsapplication.cpp:619]
user32
user32
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\core\private\windows\windowsplatformmisc.cpp:884]
UE4Editor!FEngineLoop::Tick() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\launch\private\launchengineloop.cpp:2610]
UE4Editor!GuardedMain() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\launch\private\launch.cpp:142]
UE4Editor!GuardedMainWrapper() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
UE4Editor!WinMain() [d:\buildfarm\buildmachine_++ue4+release-4.11\engine\source\runtime\launch\private\windows\launchwindows.cpp:200]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
kernel32
ntdll

Second CallStack:
UE4Editor_Engine!FStaticMeshInstanceBuffer::Init() instancedstaticmesh.cpp:93
UE4Editor_Engine!FPerInstanceRenderData::FPerInstanceRenderData() instancedstaticmesh.h:351
UE4Editor_Engine!FInstancedStaticMeshRenderData::FInstancedStaticMeshRenderData() instancedstaticmesh.h:397
UE4Editor_Engine!FInstancedStaticMeshSceneProxy::FInstancedStaticMeshSceneProxy() instancedstaticmesh.h:538
UE4Editor_Engine!FHierarchicalStaticMeshSceneProxy::FHierarchicalStaticMeshSceneProxy() hierarchicalinstancedstaticmesh.cpp:669
UE4Editor_Engine!UHierarchicalInstancedStaticMeshComponent::CreateSceneProxy() hierarchicalinstancedstaticmesh.cpp:2443
UE4Editor_Renderer!FScene::AddPrimitive() rendererscene.cpp:496
UE4Editor_Engine!UPrimitiveComponent::CreateRenderState_Concurrent() primitivecomponent.cpp:369
UE4Editor_Engine!UActorComponent::RecreateRenderState_Concurrent() actorcomponent.cpp:1163
UE4Editor_Engine!UActorComponent::DoDeferredRenderUpdates_Concurrent() actorcomponent.cpp:1240
UE4Editor_Engine!<lambda_84b416b78a7316bd7ac57fafc72715e1>::operator() leveltick.cpp:855
UE4Editor_Engine!UWorld::SendAllEndOfFrameUpdates() leveltick.cpp:872
UE4Editor_Renderer!FRendererModule::BeginRenderingViewFamily() scenerendering.cpp:1807
UE4Editor_UnrealEd!FEditorViewportClient::Draw() editorviewportclient.cpp:3068
UE4Editor_Engine!FViewport::Draw() unrealclient.cpp:1053
UE4Editor_UnrealEd!UEditorEngine::UpdateSingleViewportClient() editorengine.cpp:1715
UE4Editor_UnrealEd!UEditorEngine::Tick() editorengine.cpp:1462
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() unrealedengine.cpp:370
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:2643
UE4Editor!GuardedMain() launch.cpp:142
UE4Editor!GuardedMainWrapper() launchwindows.cpp:126
UE4Editor!WinMain() launchwindows.cpp:200
UE4Editor!__scrt_common_main_seh() exe_common.inl:264
kernel32!<Unknown>
ntdll!<Unknown>