The level blueprint has a macro that references a level.
FBlueprintNodeTemplateCache keeps holding this cashe at transition level.
Cmd: MAP LOAD FILE="../../../../MacroMemoryLeak/Content/ThirdPersonBP/Maps/ThirdPersonExampleMap.umap" TEMPLATE=0 SHOWPROGRESS=1 FEATURELEVEL=3 LightingResults: New page: Lighting Build LoadErrors: New page: Loading map: ThirdPersonExampleMap.umap LogWorld: UWorld::CleanupWorld for ThirdPersonExampleMap, bSessionEnded=true, bCleanupResources=true MapCheck: New page: Map Check LightingResults: New page: Lighting Build LogUObjectHash: Compacting FUObjectHashTables data took 3.06ms LogReferenceChain: (root) GCObjectReferencer /Engine/Transient.GCObjectReferencer_0::AddReferencedObjects(): FBlueprintNodeTemplateCache LogReferenceChain: K2Node_MacroInstance /Engine/Transient.PROTO_BP_Blueprint_0:UserConstructionScript.K2Node_MacroInstance_23->MacroGraph LogReferenceChain: EdGraph /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap.NewMacro_0->Outer LogReferenceChain: LevelScriptBlueprint /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap->Outer LogReferenceChain: Level /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel->Outer LogReferenceChain: World /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap LogReferenceChain: LogEditorServer: Error: Old world /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap not cleaned up by garbage collection while loading new map! Referenced by: (root) GCObjectReferencer /Engine/Transient.GCObjectReferencer_0::AddReferencedObjects(): FBlueprintNodeTemplateCache K2Node_MacroInstance /Engine/Transient.PROTO_BP_Blueprint_0:UserConstructionScript.K2Node_MacroInstance_23->MacroGraph EdGraph /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap.NewMacro_0->Outer LevelScriptBlueprint /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap->Outer Level /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel->Outer World /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap LogReferenceChain: (root) GCObjectReferencer /Engine/Transient.GCObjectReferencer_0::AddReferencedObjects(): FBlueprintNodeTemplateCache LogReferenceChain: K2Node_MacroInstance /Engine/Transient.PROTO_BP_Blueprint_0:UserConstructionScript.K2Node_MacroInstance_23->MacroGraph LogReferenceChain: EdGraph /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap.NewMacro_0->Outer LogReferenceChain: LevelScriptBlueprint /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap->GeneratedClass LogReferenceChain: BlueprintGeneratedClass /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap_C->Outer LogReferenceChain: Package /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap LogReferenceChain: LogEditorServer: Error: Old level package /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap not cleaned up by garbage collection while loading new map! Referenced by: (root) GCObjectReferencer /Engine/Transient.GCObjectReferencer_0::AddReferencedObjects(): FBlueprintNodeTemplateCache K2Node_MacroInstance /Engine/Transient.PROTO_BP_Blueprint_0:UserConstructionScript.K2Node_MacroInstance_23->MacroGraph EdGraph /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap.NewMacro_0->Outer LevelScriptBlueprint /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap:PersistentLevel.ThirdPersonExampleMap->GeneratedClass BlueprintGeneratedClass /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap.ThirdPersonExampleMap_C->Outer Package /Game/ThirdPersonBP/Maps/ThirdPersonExampleMap LogOutputDevice: Warning:
[Link Removed]
UE4Editor-Core.dll!ReportAssert() [d:\dev\ue423\engine\source\runtime\core\private\windows\windowsplatformcrashcontext.cpp:582] UE4Editor-Core.dll!FWindowsErrorOutputDevice::Serialize() [d:\dev\ue423\engine\source\runtime\core\private\windows\windowserroroutputdevice.cpp:79] UE4Editor-Core.dll!FOutputDevice::LogfImpl() [d:\dev\ue423\engine\source\runtime\core\private\misc\outputdevice.cpp:71] UE4Editor-Core.dll!AssertFailedImplV() [d:\dev\ue423\engine\source\runtime\core\private\misc\assertionmacros.cpp:101] UE4Editor-Core.dll!FDebug::AssertFailed() [d:\dev\ue423\engine\source\runtime\core\private\misc\assertionmacros.cpp:455] UE4Editor-UnrealEd.dll!UEditorEngine::CheckForWorldGCLeaks() [d:\dev\ue423\engine\source\editor\unrealed\private\editorserver.cpp:1994] UE4Editor-UnrealEd.dll!UEditorEngine::EditorDestroyWorld() [d:\dev\ue423\engine\source\editor\unrealed\private\editorserver.cpp:2115] UE4Editor-UnrealEd.dll!UEditorEngine::Map_Load() [d:\dev\ue423\engine\source\editor\unrealed\private\editorserver.cpp:2469] UE4Editor-UnrealEd.dll!UEditorEngine::HandleMapCommand() [d:\dev\ue423\engine\source\editor\unrealed\private\editorserver.cpp:6085] UE4Editor-UnrealEd.dll!UEditorEngine::Exec() [d:\dev\ue423\engine\source\editor\unrealed\private\editorserver.cpp:5569] UE4Editor-UnrealEd.dll!UUnrealEdEngine::Exec() [d:\dev\ue423\engine\source\editor\unrealed\private\unrealedsrv.cpp:691] UE4Editor-UnrealEd.dll!FEditorFileUtils::LoadMap() [d:\dev\ue423\engine\source\editor\unrealed\private\filehelpers.cpp:2446] UE4Editor-AssetTools.dll!FAssetTypeActions_World::OpenAssetEditor() [d:\dev\ue423\engine\source\developer\assettools\private\assettypeactions\assettypeactions_world.cpp:32] UE4Editor-UnrealEd.dll!FAssetEditorManager::OpenEditorForAsset() [d:\dev\ue423\engine\source\editor\unrealed\private\toolkits\asseteditormanager.cpp:390] UE4Editor-AssetTools.dll!FAssetTypeActions_Base::AssetsActivated() [d:\dev\ue423\engine\source\developer\assettools\public\assettypeactions_base.h:57] UE4Editor-ContentBrowser.dll!SContentBrowser::OnAssetsActivated() [d:\dev\ue423\engine\source\editor\contentbrowser\private\scontentbrowser.cpp:2123] UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,SContentBrowser,0,void __cdecl(TArray<FAssetData,TSizedDefaultAllocator<32> > const &,enum EAssetTypeActivationMethod::Type)>::ExecuteIfSafe() [d:\dev\ue423\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:369] UE4Editor-ContentBrowser.dll!SAssetView::OnListMouseButtonDoubleClick() [d:\dev\ue423\engine\source\editor\contentbrowser\private\sassetview.cpp:4297] UE4Editor-ContentBrowser.dll!TBaseSPMethodDelegateInstance<0,SAssetView,0,void __cdecl(TSharedPtr<FAssetViewItem,0>)>::ExecuteIfSafe() [d:\dev\ue423\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:369] UE4Editor-ContentBrowser.dll!TBaseDelegate<void,TSharedPtr<FAssetViewItem,0> >::ExecuteIfBound() [d:\dev\ue423\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:673] UE4Editor-ContentBrowser.dll!SListView<TSharedPtr<FAssetViewItem,0> >::Private_OnItemDoubleClicked() [d:\dev\ue423\engine\source\runtime\slate\public\widgets\views\slistview.h:883] UE4Editor-ContentBrowser.dll!STableRow<TSharedPtr<FAssetViewItem,0> >::OnMouseButtonDoubleClick() [d:\dev\ue423\engine\source\runtime\slate\public\widgets\views\stablerow.h:334] UE4Editor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FPointerEvent,<lambda_cde3b80cdb8a457b0f09fee78051d179> >() [d:\dev\ue423\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:273] UE4Editor-Slate.dll!FSlateApplication::RoutePointerDoubleClickEvent() [d:\dev\ue423\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:6246] UE4Editor-Slate.dll!FSlateApplication::ProcessMouseButtonDoubleClickEvent() [d:\dev\ue423\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:6233] UE4Editor-Slate.dll!FSlateApplication::OnMouseDoubleClick() [d:\dev\ue423\engine\source\runtime\slate\private\framework\application\slateapplication.cpp:6203] UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() [d:\dev\ue423\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1884] UE4Editor-ApplicationCore.dll!FWindowsApplication::DeferMessage() [d:\dev\ue423\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:2332] UE4Editor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() [d:\dev\ue423\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:1560] UE4Editor-ApplicationCore.dll!FWindowsApplication::AppWndProc() [d:\dev\ue423\engine\source\runtime\applicationcore\private\windows\windowsapplication.cpp:790]
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-81839 in the post.