Engine 4.26 crashes when I want to open a Level

Hello,
I’m currently working on a Project which I want to sell later on. Yesterday everything worked really fine, no crashes lags or other things. I worked on a new 3D Model which I tested on my startup test level and It had no problem, I saved every thing and closed the Engine.
Well today I wanted to add the 3D model to another Level for which it was meant but when I tried to open the level via dubbleclick it instantly crashes the Engine, even if I just try to rightclick the Level Asset. This also happens to some other Levels but not all.
the strange thing is that in all Levels I basicly have the same thigs in it and My start up level has all assets I heve in this Project so the crashing Levels dont have anything unique in them which the others don’t also have.
this is the Crash Report:

LoginId:64ff1c6e426be4bf550bc1bbdf50a0b1
EpicAccountId:28c727bcd6a1444f8800cd6e045caf4c

Assertion failed: (Index >= 0) & (Index < ArrayNum) [File:D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 674] Array index out of bounds: 0 from an array of size 0

UE4Editor_Core
UE4Editor_Core
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_ContentBrowserAssetDataSource
UE4Editor_ContentBrowserAssetDataSource
UE4Editor_ContentBrowserAssetDataSource
UE4Editor_ContentBrowser
UE4Editor_ContentBrowser
UE4Editor_ContentBrowser
UE4Editor_ContentBrowser
UE4Editor_ContentBrowser
UE4Editor_ContentBrowser
UE4Editor_ContentBrowser
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_Slate
UE4Editor_ApplicationCore
UE4Editor_ApplicationCore
UE4Editor_ApplicationCore
UE4Editor_ApplicationCore
user32
user32
UE4Editor_ApplicationCore
UE4Editor
UE4Editor
UE4Editor
UE4Editor
UE4Editor
kernel32
ntdll

Things that I allready have tried:

  1. Since it states that it trys to read an Array I did go into my Blueprints which are placed in the Level and unhooked the ConstructionScript and so on so the BPs dont run any code.
  2. Delete the newly added 3D Model and every thing that is conected with it.
  3. Delet the Level Build Data

It is not a big deal that I can’t accses the Level since I wanted to remake it for Publishing anyway but I’m worried now that the ppl who buy this will have the same Issue and I don’t want to sell a crapy Product.

If you know anything on how to solve this Problem please let me know!