Unreal crashes on open level

Can anyone help me? I’m trying to switch levels in Unreal Engine. The map I have is just the default map, a cube with collisions turned on, and a trigger sphere with a single “open level” node connected to the “ActorBeginOverlap” node. Every time there is overlap, unreal crashes and I get this message:

Fatal error: [File:D:/Build/++UE4/Sync/Engine/Source/Editor/UnrealEd/Private/EditorEngine.cpp] [Line: 6986] Previously active world /Game/UEDPIE_0_NewMap.NewMap not cleaned up by garbage collection! Referenced by: (root) UnrealEdEngine /Engine/Transient.UnrealEdEngine_0->Trans TransBuffer /Engine/Transient.TransBuffer_0::AddReferencedObjects() (PendingKill) World /Game/UEDPIE_0_NewMap.Abia Newmap

Hello,

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Thanks