Lightmass crash after finished building and hitting save

User is reporting that the editor will crash after lightmass has finished building and they click to save the project.

Cannot reproduce locally.

User is building a large world that take 10+ hours with lots of meshes. When lighting build is complete and they hit "save" the project will crash.

Crash Reporter Link: [Link Removed]

UE4Editor_Core! FFileHandleWindows::Seek() windowsplatformfile.cpp:60
UE4Editor_Core! FArchiveFileWriterGeneric::Seek() filemanagergeneric.cpp:715
UE4Editor_Core! FArchive::SerializeCompressed() archive.cpp:690
UE4Editor_CoreUObject! FUntypedBulkData::SerializeBulkData() bulkdata.cpp:1009
UE4Editor_CoreUObject! UPackage::SavePackage() savepackage.cpp:3455
UE4Editor_UnrealEd! UEditorEngine::SavePackage() editor.cpp:4416
UE4Editor_UnrealEd! UEditorEngine::Exec_Obj() editorserver.cpp:4162
UE4Editor_UnrealEd! UEditorEngine::Exec() editorserver.cpp:5238
UE4Editor_UnrealEd! UUnrealEdEngine::Exec() unrealedsrv.cpp:742
UE4Editor_UnrealEd! SaveWorld() filehelpers.cpp:526
UE4Editor_UnrealEd! FEditorFileUtils::SaveMap() filehelpers.cpp:1994
UE4Editor_UnrealEd! InternalSavePackage() filehelpers.cpp:2346
UE4Editor_UnrealEd! FEditorFileUtils::PromptForCheckoutAndSave() filehelpers.cpp:2873
UE4Editor_UnrealEd! InternalSavePackages() filehelpers.cpp:2460
UE4Editor_UnrealEd! FEditorFileUtils::SaveDirtyPackages() filehelpers.cpp:2574
UE4Editor_MainFrame! FMainFrameHandler::CanCloseEditor() mainframehandler.h:124
UE4Editor_MainFrame! FMainFrameHandler::CloseRootWindowOverride() mainframehandler.h:143
UE4Editor_SlateCore! SWindow::RequestDestroyWindow() swindow.cpp:1055
UE4Editor_Slate! SWindowTitleBar::CloseButton_OnClicked() swindowtitlebar.h:415
UE4Editor_Slate! TMemberFunctionCaller<SWindowTitleBar,FReply() delegateinstanceinterface_variadics.h:161
UE4Editor_Slate! TTupleImpl<TIntegerSequence<> >::ApplyAfter_ExplicitReturnType<FReply,TMemberFunctionCaller<SWindowTitleBar,FReply() tuple.h:113
UE4Editor_Slate! TBaseSPMethodDelegateInstance<0,SWindowTitleBar,0,FReply __cdecl() delegateinstancesimpl_variadics.inl:282
UE4Editor_Slate! TBaseDelegate<FReply>::Execute() delegatesignatureimpl_variadics.inl:439
UE4Editor_Slate! SButton::OnMouseButtonUp() sbutton.cpp:228
UE4Editor_Slate! <lambda_de96dc3471181973108233c6db1f9843>::operator() slateapplication.cpp:3985
UE4Editor_Slate! FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_de96dc3471181973108233c6db1f9843> >() slateapplication.cpp:202
UE4Editor_Slate! FSlateApplication::ProcessMouseButtonUpEvent() slateapplication.cpp:3988
UE4Editor_Slate! FSlateApplication::OnMouseUp() slateapplication.cpp:3949
UE4Editor_Core! FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1373
UE4Editor_Core! FWindowsApplication::DeferMessage() windowsapplication.cpp:1669
UE4Editor_Core! FWindowsApplication::ProcessMessage() windowsapplication.cpp:742
UE4Editor_Core! FWindowsApplication::AppWndProc() windowsapplication.cpp:604
user32! UserCallWinProcCheckWow()
user32! DispatchMessageWorker()
UE4Editor_Core! FWindowsPlatformMisc::PumpMessages() windowsplatformmisc.cpp:774
UE4Editor! FEngineLoop::Tick() launchengineloop.cpp:2233
UE4Editor! GuardedMain() launch.cpp:142
UE4Editor! GuardedMainWrapper() launchwindows.cpp:126
UE4Editor! WinMain() launchwindows.cpp:202

Editor crashes after building light

Editor crashes ( 5 times in a row! ) when saving, after the light built is done