On start up uefn crashes and gives me an error

Fatal error: [File:D:\build++Fortnite\Sync\Engine\Source\Runtime\PakFile\Private\IPlatformFilePak.cpp] [Line: 5574] Corrupt pak index detected on pak file: …/…/…/FortniteGame/Content/Paks/pakchunkscb_ExtRefoptional-WindowsClient.pak

UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
UnrealEditorFortnite_Win64_Shipping
kernel32
ntdll

Thank you for your report! Can you please re-post using the “New Issue” option on the Issues and Bug Reporting forums? Posts with this feature are connected directly into our development team so we can quickly get to them!
For more information, such as how to get the reference ID, please check out the article here: Using the Creative and UEFN Bug Reporting Form