i keep getting this message. ive tried everything i could find online to fix this. but nothing will. this is happening while trying to open a new project.
LoginId:6a5af6f541d28fa4af06a9a2ae8bfcde
Assertion failed: bIsOptional && Property->GetElementSize() >= 256 [File:D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\Serialization\UnversionedPropertySerialization.cpp] [Line: 130]
UnrealEditor_CoreUObject
Hello there @DVS_Music !
Checking around the community, the error you are encountering (Assertion failed: bIsOptional && Property->GetElementSize() >= 256 - Only large unset optionals should hit this loading path
Clear all caches tied to failed and/or old projects, by deleting or moving contents from the following folders:
\Documents\Unreal Projects
After that, fully clear cache by deleting the folders themsels, as they will regenerate when attempting to open a new project:
\AppData\Local\UnrealEngine
If the issue persists, verify your UE build by going to the launcher, and selecting “Verify” from the dropdown menu (if verification fails, then re-install the engine)
Test by creating a new project with C++ instead of blueprints (this will bypass a few template checks)
Create a direct access to Engine\Binaries\Win64\UnrealEditor.exe and add tag “-noini”, in order to bypass initial settings
If all of the above fails, the last remaining step is a full uninstall/reinstall of all Epic software:
First, uninstall the engine, launcher, asset packs, etc
Next, open the registry directory HKEY_CURRENT_USER\Software\Epic Games\Unreal Engine\Builds, and delete any build entries
Finally, delete the folders %userprofile%\AppData\Local\UnrealEngine and %userprofile%\AppData\Local\UnrealHeaderTool
After that, no elements related to UE should be left in your system
Now, reinstall UE launcher from scratch, and only add the latest version of the engine
After the process is complete, test opening a new project
DVS_Music
June 13, 2025, 8:31am
3
hey, thanks for the help. i tried what you stated. and i am now getting a new error. this is what it is saying
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x000000dc060025b4
UnrealEditor_Core!_mi_heap_realloc_zero() [D:\build++UE5\Sync\Engine\Source\ThirdParty\mimalloc\2.0.0\src\alloc.c:622]FString::operator*'::2’::<lambda_1>::operator()() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\ShaderCompiler\ShaderCompilerJobCache.cpp:1540]LowLevelTasks::FTask::Init<UE::Tasks::Private::FTaskBase::Init’::2'::<lambda_1> >'::13’::<lambda_1>,0>::CallAndMove() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Async\Fundamental\TaskDelegate.h:171]LowLevelTasks::FScheduler::CreateWorker'::2’::<lambda_1>::operator()() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Async\Fundamental\Scheduler.cpp:188]
