UE 5.5.4 keeps crashing when i try to open a new project

Development Platform & Builds
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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
EpicAccountId:f9bdeb5cc44c42f7bf5a1698ec446d4d

Assertion failed: bIsOptional && Property->GetElementSize() >= 256 [File:D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\Serialization\UnversionedPropertySerialization.cpp] [Line: 130]
Only large unset optionals should hit this loading path

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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.

  1. 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\

  1. 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\

  1. 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)

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  1. Test by creating a new project with C++ instead of blueprints (this will bypass a few template checks)

  2. Create a direct access to Engine\Binaries\Win64\UnrealEditor.exe and add tag “-noini”, in order to bypass initial settings

  3. 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