Same error for me. I got the error after updating to 5.2.1 from 5.2. Compiling a specific actor in my project crashes the editor. I can make changes, save and restart before compiling to bypass the crash for now. I can duplicate the actor class and compile the duplicate without crashing as well.
I’m not sure how to recreate the bug to report it though. Looking through any other actors that reference it, maybe related to spawning the actor.
Assertion failed: (Parameters.DestClass->GetPropertiesSize() >= Parameters.SourceObject->GetClass()->GetPropertiesSize()) [File:D:\build\++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp] [Line: 2859] Source and destination class sizes differ. Source: SparseDelegateFunction (288) Destination: Function (264)
UnrealEditor_CoreUObject!StaticDuplicateObjectEx() [D:\build\++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp:2856]
UnrealEditor_CoreUObject!StaticDuplicateObject() [D:\build\++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp:2848]
UnrealEditor_Kismet!<lambda_1c92e0a06f96968232baf1ea8a546af9>::operator()() [D:\build\++UE5\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:2965]
UnrealEditor_Kismet!FBlueprintCompilationManagerImpl::FastGenerateSkeletonClass() [D:\build\++UE5\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:3075]
UnrealEditor_Kismet!FBlueprintCompilationManagerImpl::FlushCompilationQueueImpl() [D:\build\++UE5\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:1000]
UnrealEditor_Kismet!FBlueprintCompilationManagerImpl::CompileSynchronouslyImpl() [D:\build\++UE5\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:287]
UnrealEditor_Kismet!FBlueprintCompilationManager::CompileSynchronously() [D:\build\++UE5\Sync\Engine\Source\Editor\Kismet\Private\BlueprintCompilationManager.cpp:3370]
UnrealEditor_UnrealEd!FKismetEditorUtilities::CompileBlueprint() [D:\build\++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\Kismet2\Kismet2.cpp:763]
UnrealEditor_Kismet!FBlueprintEditor::Compile() [D:\build\++UE5\Sync\Engine\Source\Editor\Kismet\Private\BlueprintEditor.cpp:4085]
UnrealEditor_Kismet!TBaseSPMethodDelegateInstance<0,FBlueprintEditor,1,void __cdecl(void),FDefaultDelegateUserPolicy>::ExecuteIfSafe() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:292]
UnrealEditor_Slate!FUICommandList::ExecuteAction() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Commands\UICommandList.cpp:111]
UnrealEditor_Slate!SToolBarButtonBlock::OnClicked() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\MultiBox\SToolBarButtonBlock.cpp:384]
UnrealEditor_Slate!TBaseSPMethodDelegateInstance<0,SToolBarButtonBlock,1,FReply __cdecl(void),FDefaultDelegateUserPolicy>::Execute() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:275]
UnrealEditor_Slate!SButton::ExecuteOnClick() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Input\SButton.cpp:465]
UnrealEditor_Slate!SButton::OnMouseButtonUp() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Input\SButton.cpp:390]
UnrealEditor_Slate!<lambda_51e270ca99ea7ce852539efd04dd453f>::operator()() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5129]
UnrealEditor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_51e270ca99ea7ce852539efd04dd453f> >() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:420]
UnrealEditor_Slate!FSlateApplication::RoutePointerUpEvent() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5115]
UnrealEditor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5684]
UnrealEditor_Slate!FSlateApplication::OnMouseUp() [D:\build\++UE5\Sync\Engine\Source\Runtime\Slate\Private\Framework\Application\SlateApplication.cpp:5649]
UnrealEditor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2219]
UnrealEditor_ApplicationCore!FWindowsApplication::DeferMessage() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:2726]
UnrealEditor_ApplicationCore!FWindowsApplication::ProcessMessage() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:1895]
UnrealEditor_ApplicationCore!FWindowsApplication::AppWndProc() [D:\build\++UE5\Sync\Engine\Source\Runtime\ApplicationCore\Private\Windows\WindowsApplication.cpp:925]