Editor Crashes on Startup - Assertion failed: !IsInRenderingThread

I’m having issues opening my project with the engine, when I just launch the game without the editor (right click on the uproject and launch game) the map loads fine, but with editor it crashes.

The stacktrace doesn’t indicate any of my own C++ code, and I’m not sure how I triggered this (as i was working normally and closed the editor gracefully last time).

Stacktrace:

Assertion failed: !IsInRenderingThread() [File:D:/Build/++UE4+Licensee/Sync/Engine/Source/Runtime/Landscape/Private/LandscapeRenderMobile.cpp] [Line: 471]

UE4Editor_Core!AssertFailedImplV() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:100]
UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:450]
UE4Editor_Landscape!FLandscapeComponentDerivedData::GetRenderData() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Landscape\Private\LandscapeRenderMobile.cpp:471]
UE4Editor_Landscape!FLandscapeComponentSceneProxyMobile::FLandscapeComponentSceneProxyMobile() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Landscape\Private\LandscapeRenderMobile.cpp:343]
UE4Editor_Landscape!ULandscapeComponent::CreateSceneProxy() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Landscape\Private\Landscape.cpp:1404]
UE4Editor_Renderer!FScene::AddPrimitive() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Renderer\Private\RendererScene.cpp:1296]
UE4Editor_Engine!UPrimitiveComponent::CreateRenderState_Concurrent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\Components\PrimitiveComponent.cpp:574]
UE4Editor_Engine!FComponentRecreateRenderStateContext::~FComponentRecreateRenderStateContext() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Public\ComponentRecreateRenderStateContext.h:43]
UE4Editor_Engine!FGlobalComponentRecreateRenderStateContext::~FGlobalComponentRecreateRenderStateContext() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\Components\ActorComponent.cpp:210]
UE4Editor_UnrealEd!FEditorViewportClient::UpdateHiddenCollisionDrawing() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\UnrealEd\Private\EditorViewportClient.cpp:5184]
UE4Editor_UnrealEd!FEditorViewportClient::SetViewModes() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\UnrealEd\Private\EditorViewportClient.cpp:5242]
UE4Editor_LevelEditor!SLevelViewport::ConstructLevelEditorViewportClient() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\SLevelViewport.cpp:533]
UE4Editor_LevelEditor!SLevelViewport::Construct() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\SLevelViewport.cpp:190]
UE4Editor_LevelEditor!TDecl<SLevelViewport,RequiredArgs::T0RequiredArgs>::operator<<=() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\SlateCore\Public\Widgets\DeclarativeSyntaxSupport.h:1122]
UE4Editor_LevelEditor!FLevelViewportLayoutEntity::FLevelViewportLayoutEntity() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelViewportLayoutEntity.cpp:11]
UE4Editor_LevelEditor!<lambda_dfdf02bcfdaea964b9de41d2b6874ec9>::operator()() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Public\ViewportTypeDefinition.h:20]
UE4Editor_LevelEditor!UE4Function_Private::TFunctionRefCaller<<lambda_dfdf02bcfdaea964b9de41d2b6874ec9>,TSharedRef<ILevelViewportLayoutEntity,0> __cdecl(FViewportConstructionArgs const &)>::Call() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Public\Templates\Function.h:539]
UE4Editor_LevelEditor!FLevelEditorModule::FactoryViewport() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelEditor.cpp:626]
UE4Editor_LevelEditor!FLevelViewportLayout2x2::MakeViewportLayout() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelViewportLayout2x2.cpp:74]
UE4Editor_LevelEditor!FLevelViewportLayout::BuildViewportLayout() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelViewportLayout.cpp:205]
UE4Editor_LevelEditor!FLevelViewportTabContent::UpdateViewportTabWidget() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelViewportTabContent.cpp:162]
UE4Editor_LevelEditor!FLevelViewportTabContent::Initialize() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelViewportTabContent.cpp:62]
UE4Editor_LevelEditor!SLevelEditor::BuildViewportTab() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\SLevelEditor.cpp:976]
UE4Editor_LevelEditor!SLevelEditor::SpawnLevelEditorTab() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\SLevelEditor.cpp:632]
UE4Editor_LevelEditor!TBaseSPMethodDelegateInstance<0,SLevelEditor,0,TSharedRef<SDockTab,0> __cdecl(FSpawnTabArgs const &),FName,FString>::Execute() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:298]
UE4Editor_Slate!FTabManager::SpawnTab() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1673]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1420]
UE4Editor_Slate!FTabManager::CanRestoreSplitterContent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1586]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1544]
UE4Editor_Slate!FTabManager::CanRestoreSplitterContent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1586]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1544]
UE4Editor_Slate!FTabManager::CanRestoreSplitterContent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1586]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1544]
UE4Editor_Slate!FTabManager::CanRestoreSplitterContent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1586]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1516]
UE4Editor_Slate!FTabManager::RestoreArea() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1357]
UE4Editor_Slate!FTabManager::RestoreFrom() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:863]
UE4Editor_LevelEditor!SLevelEditor::RestoreContentArea() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\SLevelEditor.cpp:1390]
UE4Editor_LevelEditor!SLevelEditor::Initialize() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\SLevelEditor.cpp:208]
UE4Editor_LevelEditor!FLevelEditorModule::SpawnLevelEditor() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\LevelEditor\Private\LevelEditor.cpp:205]
UE4Editor_LevelEditor!TBaseRawMethodDelegateInstance<0,FLevelEditorModule,TSharedRef<SDockTab,0> __cdecl(FSpawnTabArgs const &)>::Execute() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:486]
UE4Editor_Slate!FTabManager::SpawnTab() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1673]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1420]
UE4Editor_Slate!FTabManager::CanRestoreSplitterContent() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1586]
UE4Editor_Slate!FTabManager::RestoreArea_Helper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1516]
UE4Editor_Slate!FTabManager::RestoreArea() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:1357]
UE4Editor_Slate!FTabManager::RestoreFrom() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Slate\Private\Framework\Docking\TabManager.cpp:863]
UE4Editor_MainFrame!FMainFrameModule::CreateDefaultMainFrame() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\MainFrame\Private\MainFrameModule.cpp:223]
UE4Editor_UnrealEd!EditorInit() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdGlobals.cpp:144]
UE4Editor!GuardedMain() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:149]
UE4Editor!GuardedMainWrapper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137]
UE4Editor!WinMain() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:268]
UE4Editor!__scrt_common_main_seh() [d:\agent\_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll

I tried deleting Binary and Intermediate directories to rebuild the project, didn’t help.

Something curious - I reverted my recent progress from VCS (to a recently working commit), and it still crashes,

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