This is new for 4.5 preview, does not happen in 4.4.3. Reproducible project attached - just browse to the animation sequence and try to open it: Project zip (I can provide the source FBX if needed)
I’m geting an assert inside AnimationSequence.cpp:801:
const int32 PoseBoneIndex = SkeletonToPoseBoneIndexArray[SkeletonBoneIndex];
Because SkeletonBoneIndex is 14, and the array is size 5 (there are 5 bones in the Skeleton).
The source build call stack:
UE4Editor-Core-Win64-Debug.dll!StaticFailDebug(const wchar_t * Error, const char * File, int Line, const wchar_t * Description, bool bIsEnsure) Line 186 C++ UE4Editor-Core-Win64-Debug.dll!FDebug::AssertFailed(const char * Expr, const char * File, int Line, const wchar_t * Format, ...) Line 220 C++ UE4Editor-Engine-Win64-Debug.dll!UAnimSequence::GetBonePose(TArray & OutAtoms, const FBoneContainer & RequiredBones, const FAnimExtractContext & ExtractionContext) Line 801 C++ UE4Editor-Engine-Win64-Debug.dll!UAnimSequence::GetAnimationPose(TArray & OutAtoms, const FBoneContainer & RequiredBones, const FAnimExtractContext & ExtractionContext) Line 677 C++ UE4Editor-Engine-Win64-Debug.dll!FAnimationRuntime::GetPoseFromSequence(const UAnimSequenceBase * InSequence, const FBoneContainer & RequiredBones, TArray & ResultAtoms, const FAnimExtractContext & ExtractionContext) Line 383 C++ UE4Editor-Engine-Win64-Debug.dll!FAnimationRuntime::GetPoseFromBlendSpace(UBlendSpaceBase * BlendSpace, TArray & BlendSampleDataCache, FBoneContainer & RequiredBones, TArray & ResultAtoms) Line 590 C++ UE4Editor-Engine-Win64-Debug.dll!UAnimSingleNodeInstance::InternalBlendSpaceEvaluatePose(UBlendSpaceBase * BlendSpace, TArray & BlendSampleDataCache, FA2Pose & Pose) Line 604 C++ UE4Editor-Engine-Win64-Debug.dll!UAnimSingleNodeInstance::NativeEvaluateAnimation(FPoseContext & Output) Line 313 C++ UE4Editor-Engine-Win64-Debug.dll!UAnimInstance::EvaluateAnimation(FPoseContext & Output) Line 483 C++ UE4Editor-Engine-Win64-Debug.dll!USkeletalMeshComponent::EvaluateAnimation(const USkeletalMesh * InSkeletalMesh, UAnimInstance * InAnimInstance, TArray & OutLocalAtoms, TArray & OutVertexAnims, FVector & OutRootBoneTranslation) Line 839 C++ UE4Editor-Engine-Win64-Debug.dll!USkeletalMeshComponent::PerformAnimationEvaluation(const USkeletalMesh * InSkeletalMesh, UAnimInstance * InAnimInstance, TArray & OutSpaceBases, TArray & OutLocalAtoms, TArray & OutVertexAnims, FVector & OutRootBoneTranslation) Line 904 C++ UE4Editor-Engine-Win64-Debug.dll!USkeletalMeshComponent::RefreshBoneTransforms(FActorComponentTickFunction * TickFunction) Line 980 C++ UE4Editor-UnrealEd-Win64-Debug.dll!FBlendSpaceThumbnailScene::SetBlendSpace(UBlendSpaceBase * InBlendSpace) Line 678 C++ UE4Editor-UnrealEd-Win64-Debug.dll!UBlendSpaceThumbnailRenderer::Draw(UObject * Object, int X, int Y, unsigned int Width, unsigned int Height, FRenderTarget * RenderTarget, FCanvas * Canvas) Line 26 C++ UE4Editor-UnrealEd-Win64-Debug.dll!ThumbnailTools::RenderThumbnail(UObject * InObject, const unsigned int InImageWidth, const unsigned int InImageHeight, ThumbnailTools::EThumbnailTextureFlushMode::Type InFlushMode, FTextureRenderTargetResource * InTextureRenderTargetResource, FObjectThumbnail * OutThumbnail) Line 3460 C++ UE4Editor-UnrealEd-Win64-Debug.dll!FAssetThumbnailPool::Tick(float DeltaTime) Line 893 C++ UE4Editor-ContentBrowser-Win64-Debug.dll!SAssetView::Tick(const FGeometry & AllottedGeometry, const double InCurrentTime, const float InDeltaTime) Line 905 C++ UE4Editor-SlateCore-Win64-Debug.dll!SWidget::TickWidgetsRecursively(const FGeometry & AllottedGeometry, const double InCurrentTime, const float InDeltaTime) Line 257 C++
The launcher build stack:
MachineId:C1809C3F42407506509549AD98DA448F EpicAccountId:01c53909253245dbaebe6606e81b65cb Unknown exception - code 00000001 (first/second chance not available) Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.5\Engine\Source\Runtime\Core\Public\Containers\Array.h] [Line: 536] Array index out of bounds: 14 from an array of size 5 KERNELBASE + 23544 bytes UE4Editor_Core + 3175412 bytes UE4Editor_Core + 1678104 bytes UE4Editor_Core + 1567474 bytes UE4Editor_Engine + 11266833 bytes UE4Editor_Engine + 11263283 bytes UE4Editor_Engine + 10916123 bytes UE4Editor_Engine + 11309201 bytes UE4Editor_AnimGraph + 245275 bytes UE4Editor_Engine + 10837371 bytes UE4Editor_Engine + 7189081 bytes UE4Editor_Engine + 7352975 bytes UE4Editor_Engine + 7381168 bytes UE4Editor_UnrealEd + 6412993 bytes UE4Editor_Engine + 8156876 bytes UE4Editor_Engine + 7448542 bytes UE4Editor_Engine + 1589383 bytes UE4Editor_Engine + 1651174 bytes UE4Editor_Engine + 8778950 bytes UE4Editor_Engine + 8828651 bytes UE4Editor_Core + 749748 bytes UE4Editor_Core + 750141 bytes UE4Editor_Core + 873493 bytes UE4Editor_Engine + 9059541 bytes UE4Editor_Engine + 8970665 bytes UE4Editor_Engine + 8981525 bytes UE4Editor_Engine + 5590310 bytes UE4Editor_Engine + 5619039 bytes UE4Editor_Persona + 1142235 bytes UE4Editor_UnrealEd + 1896152 bytes UE4Editor_UnrealEd + 6486294 bytes UE4Editor!FEngineLoop::Tick() + 3524 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.5\engine\source\runtime\launch\private\launchengineloop.cpp:2129] UE4Editor!GuardedMain() + 479 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.5\engine\source\runtime\launch\private\launch.cpp:133] UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.5\engine\source\runtime\launch\private\windows\launchwindows.cpp:125] UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.5\engine\source\runtime\launch\private\windows\launchwindows.cpp:201] UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]