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Crash when using tiled landscape in Map.h

I sometimes get following crash while using a tiled landscape in ue 4.26

Assertion failed: Pair != nullptr [File:D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Map.h] [Line: 621]

UE4Editor_Core!AssertFailedImplV() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:102]
UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:458]
UE4Editor_Landscape!FLandscapeNeighborInfo::RegisterNeighbors() [D:\Build++UE4\Sync\Engine\Source\Runtime\Landscape\Private\LandscapeRender.cpp:4498]
UE4Editor_Renderer!FScene::OnLevelAddedToWorld_RenderThread() [D:\Build++UE4\Sync\Engine\Source\Runtime\Renderer\Private\RendererScene.cpp:3620]
UE4Editor_Renderer!TEnqueueUniqueRenderCommandType<FScene::OnLevelAddedToWorld'::2’::FLevelAddedToWorldName,<lambda_5efb62cc65a4fc08e132722ed967a4f6> >::DoTask() [D:\Build++UE4\Sync\Engine\Source\Runtime\RenderCore\Public\RenderingThread.h:183]
UE4Editor_Renderer!TGraphTask<TEnqueueUniqueRenderCommandType<FScene::OnLevelAddedToWorld'::2’::FLevelAddedToWorldName,<lambda_5efb62cc65a4fc08e132722ed967a4f6> > >::ExecuteTask() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Async\TaskGraphInterfaces.h:886]
UE4Editor_Core!FNamedTaskThread::ProcessTasksNamedThread() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:709]
UE4Editor_Core!FNamedTaskThread::ProcessTasksUntilQuit() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Async\TaskGraph.cpp:601]
UE4Editor_RenderCore!RenderingThreadMain() [D:\Build++UE4\Sync\Engine\Source\Runtime\RenderCore\Private\RenderingThread.cpp:373]
UE4Editor_RenderCore!FRenderingThread::Run() [D:\Build++UE4\Sync\Engine\Source\Runtime\RenderCore\Private\RenderingThread.cpp:509]
UE4Editor_Core!FRunnableThreadWin::Run() [D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Private\Windows\WindowsRunnableThread.cpp:86]

How can I see what is causing this crash?

It tells you in what you pasted.
Something referencing something has an invalid reference causing the pointer to be null.

Find Engine\Source\Runtime\Core\Public\Containers/Map.h, check line 621.
From there, with the function name you can try to find whoever or whatever is calling the function with an improper function call by painfully sifting though the code.

Or, pack your map up in a sample project and submit a bug report with it so that someone at epic can do the job of sifting though and repairing whatever is calling the function without a reference.

Same crash and error with world composition. Did you submit the bug?

@Haoris i could not upload a bug, Epics Bug Tracker does not work for me. Can you do it?
Btw: what landscape scale are you using?