Editor crash (0xc0000005 / null deref) switching to StateTree tab after stopping PIE while detached (F8) and a Vehicle pawn is selected

General Issues and Bug Reporting (Unreal Engine)
1

Summary

The editor crashes with an access violation reading address 0x28 when
switching to an open StateTree asset tab immediately after stopping
Play-In-Editor, if the editor viewport was detached (F8) and the possessed
Vehicle pawn was selected before PIE was stopped.

This appears specific to the Vehicle pawn/game mode. In the same project,
switching the game mode to Third Person and possessing the default
ThirdPerson character, the identical sequence (PIE, F8 detach, select
possessed character, stop PIE, switch to StateTree tab) does NOT crash and
does not even produce the degraded-toolbar symptom. Importing the Vehicle
template into that same project and switching the game mode to Vehicle
reproduces the crash reliably with the same steps. Selecting a non-Actor
object (e.g. a static mesh) while detached also does not reproduce it.

If the viewport is re-attached (F8 again) before stopping PIE, no crash
occurs, but the StateTree toolbar renders in a visibly incomplete state
(missing “New Task”/“New Condition”/“New Consideration” buttons) until the
tab is closed and reopened — this appears to be a related, non-fatal
instance of the same underlying issue.

Reproduced in an existing production project and, separately, in a clean
Vehicle template project (UE 5.6.1, no third-party plugins), so this is not
project-specific — it is specific to the Vehicle pawn/game mode.

What Type of Bug are you experiencing?

AI

Steps to Reproduce

Steps to Reproduce:

  1. Open (or import) Epic’s Vehicle template, with the Vehicle game mode set
    as default, in a UE 5.6.1 project.
  2. Create any StateTree asset (contents don’t matter) and keep it open in
    its own editor tab.
  3. Start Play In Editor.
  4. Press F8 to detach from the possessed Vehicle pawn.
  5. Click/select the possessed Vehicle actor in the detached viewport.
  6. Stop Play In Editor while still detached and the vehicle still selected.
  7. Switch focus to the StateTree asset tab (click the tab, or Ctrl+Tab to
    it).
  8. Editor crashes immediately.

Expected Result

Switching to the StateTree tab after stopping PIE should not crash the
editor, regardless of pawn/game mode, viewport attach state, or actor
selection.

Observed Result

EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000028

Affects Versions

5.6

Platform(s)

Windows

For crash reports, include your callstack

Fatal error!

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000028

0x00007ff8b2eec9da UnrealEditor-InteractiveToolsFramework.dll!UInteractiveToolManager::GetContextObjectStore() [D:\build++UE5\Sync\Engine\Source\Runtime\InteractiveToolsFramework\Private\InteractiveToolManager.cpp:431]
0x00007ff83461f618 UnrealEditor-StateTreeEditorModule.dll!UStateTreeEditorMode::IsCompileVisible() [D:\build++UE5\Sync\Engine\Plugins\Runtime\StateTree\Source\StateTreeEditorModule\Private\StateTreeEditorMode.cpp:452]
0x00007ff8345fe7c0 UnrealEditor-StateTreeEditorModule.dll!V::TBaseUObjectMethodDelegateInstance::Execute() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:673]
0x00007ff8de8d47f1 UnrealEditor-Slate.dll!FUICommandList::GetVisibility() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Commands\UICommandList.cpp:155]
0x00007ff8de9c7724 UnrealEditor-Slate.dll!SToolBarButtonBlock::GetBlockVisibility() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\MultiBox\SToolBarButtonBlock.cpp:620]
0x00007ff8de9b9735 UnrealEditor-Slate.dll!V::TBaseSPMethodDelegateInstance::Execute() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:292]
0x00007ff8de3c8242 UnrealEditor-SlateCore.dll!SlateAttributePrivate::TSlateAttributeBase<SWidget,EVisibility,SlateAttributePrivate::FSlateAttributeNoInvalidationReason,TSlateAttributeComparePredicate<TEqualTo >,0>::FSlateAttributeGetterWrapper<SlateAttributePrivate::TSlateAttributeBase<SWidget,EVisibility,SlateAttributePrivate::FSlateAttributeNoInvalidationReason,TSlateAttributeComparePredicate<TEqualTo >,0> >::UpdateAttribute() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Public\Types\Attributes\SlateAttributeBase.inl:584]
0x00007ff8de3c885c UnrealEditor-SlateCore.dll!FSlateAttributeMetaData::UpdateAttributesImpl() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Types\SlateAttributeMetaData.cpp:492]
0x00007ff8de3b62ad UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3b63a1 UnrealEditor-SlateCore.dll!SWidget::Prepass_ChildLoop() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1810]
0x00007ff8de3b64a2 UnrealEditor-SlateCore.dll!SWidget::Prepass_Internal() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1750]
0x00007ff8de3c3942 UnrealEditor-SlateCore.dll!SWidget::SlatePrepass() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:704]
0x00007ff8de82983d UnrealEditor-Slate.dll!PrepassWindowAndChildren() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:1272]
0x00007ff8de80b649 UnrealEditor-Slate.dll!FSlateApplication::DrawPrepass() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:1323]
0x00007ff8de82a2a7 UnrealEditor-Slate.dll!FSlateApplication::PrivateDrawWindows() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:1375]
0x00007ff8de80c198 UnrealEditor-Slate.dll!FSlateApplication::DrawWindows() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:1121]
0x00007ff8de84a57d UnrealEditor-Slate.dll!FSlateApplication::TickAndDrawWidgets() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:1726]
0x00007ff8de849ab0 UnrealEditor-Slate.dll!FSlateApplication::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:1576]
0x00007ff6cc97b41a UnrealEditor.exe!FEngineLoop::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5751]
0x00007ff6cc99e5ac UnrealEditor.exe!GuardedMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:187]
0x00007ff6cc99e6ba UnrealEditor.exe!GuardedMainWrapper() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:128]
0x00007ff6cc9a209e UnrealEditor.exe!LaunchWindowsStartup() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:282]
0x00007ff6cc9b4e44 UnrealEditor.exe!WinMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:339]
0x00007ff6cc9b80fa UnrealEditor.exe!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
0x00007ff942917374 KERNEL32.DLL!UnknownFunction

Additional Notes

  • Confirmed NOT to reproduce with the Third Person template/game mode and
    default ThirdPerson character, using the identical steps in the same
    project — appears specific to the Vehicle pawn/game mode.
  • Step 4 (F8 detach) before stopping PIE is required.
  • Step 5 (selecting the possessed Vehicle actor specifically, while
    detached) is required — selecting a non-Actor object does not reproduce
    the crash.
  • If F8 is pressed again to re-attach before stopping PIE (undoing step 4),
    no crash occurs, but the StateTree toolbar shows a stripped/incomplete
    set of buttons until the tab is closed and reopened — likely the same
    underlying issue in a non-fatal form.