FMeshMergeHelpers::RetrieveMesh crashes when trying to prep some skeletal meshes for material baking.
Assertion failed: (Index >= 0) & (Index < ArrayNum) File:D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h [Line: 674] Array index out of bounds: 32 from an array of size 32 UE4Editor_Core!AssertFailedImplV() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:104] UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:461] UE4Editor_MeshMergeUtilities!DispatchCheckVerify<void,<lambda_b5c14ef3884adafb7fe831c17abccdec> >() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Misc\AssertionMacros.h:165] UE4Editor_MeshMergeUtilities!FMeshMergeHelpers::RetrieveMesh() [D:\Build\++UE4\Sync\Engine\Source\Developer\MeshMergeUtilities\Private\MeshMergeHelpers.cpp:332] UE4Editor_MeshMergeUtilities!FMeshMergeUtilities::BakeMaterialsForComponent() [D:\Build\++UE4\Sync\Engine\Source\Developer\MeshMergeUtilities\Private\MeshMergeUtilities.cpp:145] UE4Editor_MeshMergeUtilities!FMeshMergeUtilities::BakeMaterialsForComponent() [D:\Build\++UE4\Sync\Engine\Source\Developer\MeshMergeUtilities\Private\MeshMergeUtilities.cpp:459] UE4Editor_MeshMergeUtilities!<lambda_747c8298733ede9d136621237275d741>::operator()() [D:\Build\++UE4\Sync\Engine\Source\Developer\MeshMergeUtilities\Private\MeshMergeEditorExtensions.cpp:113] UE4Editor_MeshMergeUtilities!TBaseFunctorDelegateInstance<void _cdecl(FToolMenuContext const &),FDefaultDelegateUserPolicy,<lambda_747c8298733ede9d136621237275d741> >::ExecuteIfSafe() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:838] UE4Editor_ToolMenus!TBaseFunctorDelegateInstance<void __cdecl(void),FDefaultDelegateUserPolicy,<lambda_fccc1bd4ef83d8f2198f8e70891f6d41> >::ExecuteIfSafe() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:839] UE4Editor_Slate!SToolBarButtonBlock::OnClicked() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\MultiBox\SToolBarButtonBlock.cpp:308] UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SToolBarButtonBlock,0,FReply __cdecl(void),FDefaultDelegateUserPolicy>::Execute() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:290] UE4Editor_Slate!SButton::ExecuteOnClick() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Input\SButton.cpp:385] UE4Editor_Slate!SButton::OnMouseButtonUp() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Input\SButton.cpp:304] UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_cc5aea9e7377b04ce85c30c65ec3889b> >() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:378] UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:4815] UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5356] UE4Editor_Slate!FSlateApplication::OnMouseUp() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5321] UE4Editor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2178] UE4Editor_ApplicationCore!FWindowsApplication::DeferMessage() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2642] UE4Editor_ApplicationCore!FWindowsApplication::ProcessMessage() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:1046] UE4Editor_ApplicationCore!FWindowsApplication::AppWndProc() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:878] user32 user32 UE4Editor_ApplicationCore!FWindowsPlatformApplicationMisc::PumpMessages() [D:\Build\++UE4\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsPlatformApplicationMisc.cpp:130] UE4Editor!FEngineLoop::Tick() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:4748] UE4Editor!GuardedMain() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:169] UE4Editor!GuardedMainWrapper() [D:\Build\++UE4\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137] UE4Editor!WinMain() [D:\Build\++UE4\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
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-118707 in the post.