Unreal Engine Issues and Bug Tracker (UE-172971)

Description

Attempting to merge two spline actors causes the Engine to crash. This issue occurs with the Steps to Reproduce regardless if there are more branches added to the tree branch spline/enabled, and regardless if the two splines have already been connected or not (i.e. one nested under the other in the Outliner). I confirmed that mergng splines in 5.0.3 does work, making this a regression. I was unable to determine a suitable workaround for this issue, and reproduced the crash 6/6 times.

Steps to Reproduce

Obtain "Procedural Nature Pack Vol. 1" from the Unreal Engine Marketplace (should be free to get)
Open or create a new 5.1 Project
Add the "Procedural Nature Pack Vol. 1" to the project
In the Content Browser, navigate to ProceduralNaturePack > Spline_BluePrints
Drag two master_tree_branch_spline blueprints into the level
Select both assets (shift + click on both of them) then navigate to Actor > Merge actors (2) > Merge
Click "Save" on the Create Merged Actor window

Result: The Editor crashes and does not create the merged asset.
Expected: The Editor does not crash and an asset is created that merges the two selected splines.

Callstack

[2022.12.14-22.02.42:046][890]LogWindows: Error: Fatal error!
[2022.12.14-22.02.42:046][890]LogWindows: Error: 
[2022.12.14-22.02.42:046][890]LogWindows: Error: Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000008
[2022.12.14-22.02.42:046][890]LogWindows: Error: 
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd15857d51 UnrealEditor-MeshMergeUtilities.dll!FMeshMergeHelpers::FixupNonStandaloneMaterialReferences() [D:\build\++UE5\Sync\Engine\Source\Developer\MeshMergeUtilities\Private\MeshMergeHelpers.cpp:1227]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd15864fd2 UnrealEditor-MeshMergeUtilities.dll!FMeshMergeUtilities::MergeComponentsToStaticMesh() [D:\build\++UE5\Sync\Engine\Source\Developer\MeshMergeUtilities\Private\MeshMergeUtilities.cpp:3089]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffcfd151156 UnrealEditor-MergeActors.dll!FMeshMergingTool::RunMerge() [D:\build\++UE5\Sync\Engine\Source\Editor\MergeActors\Private\MeshMergingTool\MeshMergingTool.cpp:129]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffcfd1525c6 UnrealEditor-MergeActors.dll!FMergeActorsTool::RunMergeFromSelection() [D:\build\++UE5\Sync\Engine\Source\Editor\MergeActors\Private\MergeActorsTool.cpp:29]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd1dac499e UnrealEditor-LevelEditor.dll!TBaseFunctorDelegateInstance<void __cdecl(void),FDefaultDelegateUserPolicy,<lambda_a07033b35d316ea30d074a1bf5551212> >::ExecuteIfSafe() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:847]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dd61260 UnrealEditor-Slate.dll!SMenuEntryBlock::OnClicked() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\MultiBox\SMenuEntryBlock.cpp:1157]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dd65460 UnrealEditor-Slate.dll!SMenuEntryBlock::OnMenuItemButtonClicked() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\MultiBox\SMenuEntryBlock.cpp:1108]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dd397c4 UnrealEditor-Slate.dll!TBaseSPMethodDelegateInstance<0,SMenuEntryBlock,1,FReply __cdecl(void),FDefaultDelegateUserPolicy>::Execute() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:295]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dde05f6 UnrealEditor-Slate.dll!SButton::ExecuteOnClick() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Input\SButton.cpp:465]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4de06793 UnrealEditor-Slate.dll!SButton::OnMouseButtonUp() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Input\SButton.cpp:390]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dd66e8c UnrealEditor-Slate.dll!SMenuEntryButton::OnMouseButtonUp() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\MultiBox\SMenuEntryBlock.cpp:434]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4db9a3e8 UnrealEditor-Slate.dll!<lambda_51e270ca99ea7ce852539efd04dd453f>::operator()() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5046]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4db7ffca UnrealEditor-Slate.dll!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_51e270ca99ea7ce852539efd04dd453f> >() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:412]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dbe6743 UnrealEditor-Slate.dll!FSlateApplication::RoutePointerUpEvent() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5032]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dbd5223 UnrealEditor-Slate.dll!FSlateApplication::ProcessMouseButtonUpEvent() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5601]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffd4dbcaecc UnrealEditor-Slate.dll!FSlateApplication::OnMouseUp() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5566]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffda09e19a2 UnrealEditor-ApplicationCore.dll!FWindowsApplication::ProcessDeferredMessage() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2219]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffda09c67d1 UnrealEditor-ApplicationCore.dll!FWindowsApplication::DeferMessage() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2726]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffda09e4391 UnrealEditor-ApplicationCore.dll!FWindowsApplication::ProcessMessage() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:1895]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffda09bff93 UnrealEditor-ApplicationCore.dll!FWindowsApplication::AppWndProc() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:925]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffdc429e858 USER32.dll!UnknownFunction []
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffdc429e299 USER32.dll!UnknownFunction []
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffda09e5849 UnrealEditor-ApplicationCore.dll!FWindowsPlatformApplicationMisc::PumpMessages() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsPlatformApplicationMisc.cpp:142]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ff6f09b7332 UnrealEditor.exe!FEngineLoop::Tick() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5291]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ff6f09d287d UnrealEditor.exe!GuardedMain() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:202]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ff6f09d296a UnrealEditor.exe!GuardedMainWrapper() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:107]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ff6f09d5680 UnrealEditor.exe!LaunchWindowsStartup() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:244]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ff6f09e71b4 UnrealEditor.exe!WinMain() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:282]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ff6f09ea516 UnrealEditor.exe!__scrt_common_main_seh() [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffdc41e7034 KERNEL32.DLL!UnknownFunction []
[2022.12.14-22.02.42:046][890]LogWindows: Error: [Callstack] 0x00007ffdc60226a1 ntdll.dll!UnknownFunction []
[2022.12.14-22.02.42:046][890]LogWindows: Error:

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Unresolved

Component	UE - World Creation - Worldbuilding Tools - Merge Actor
Affects Versions	5.1
Target Fix	5.6

Created	Dec 15, 2022
Updated	Oct 11, 2024

View Jira Issue

UE-172971

Merging Splines causes Engine to Crash in 5.1

Merging Splines causes Engine to Crash in 5.1

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