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) has popped up in other threads, and its usually tied to UE attempting to reach a corrupted default asset, or a template trying to access an invalid property, both normal processes when opening new projects. Let’s try a few steps for resolution.
- Clear all caches tied to failed and/or old projects, by deleting or moving contents from the following folders:
\Documents\Unreal Projects
\AppData\Local\UnrealEngine\
- After that, fully clear cache by deleting the folders themsels, as they will regenerate when attempting to open a new project:
\AppData\Local\UnrealEngine
\AppData\Roaming\Unreal Engine\
- 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