Unreal crash at 18% even after deleting projects and redownloading the engine

Development Platform & Builds
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1

I am using Unreal to build a sample game for a scholarship and now it is broken. I was making the project when i decided that i had reached the end of my productivity so i decided to start a new project to unwind and build some landscapes but unreal crashed when i tried to open it. i figured it was something to do with how i had two instances running(the original project and the new one) so i saved and closed the original project and tried again with the same result. i then figured it was something to do with my old project so i tried moving and temporarily deleting my project but had the same result so i made a backup of my project and deleted it from the projects page in the epic games launcher but it still crashed at 18 percent. i was getting desperate so i re downloaded the entire engine and now it still has the same crash. the crash screen says this:

Assertion failed: SerializeNum >= 0 [File:D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h] [Line: 1152]

UE4Editor_Core
UE4Editor_Core
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_Engine
UE4Editor
UE4Editor
UE4Editor
UE4Editor
UE4Editor
kernel32
ntdll

the crash has never varied regardless of what i do
any suggestions or fixes?

2

I am getting the same error

Assertion failed: SerializeNum >= 0
[File:D:\Build++UE4\Sync\Engine\Source\Runtime\Core\Public\Containers/Array.h]
[Line: 1152]

UE4Editor_Core UE4Editor_Core
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_DerivedDataCache
UE4Editor_Core UE4Editor_Core
UE4Editor_Core UE4Editor_Core
UE4Editor_Engine UE4Editor UE4Editor
UE4Editor UE4Editor UE4Editor kernel32
ntdll

3

Hey not sure if you guys are still having this issue, but I’ve found something that fixed it for me. In the file explorer go to Appdata → local → Unreal engine-> 4.25. Then once there delete the derived data cache folder.Then when you launch UE4 it shouldn’t crash.
Hope this helps.

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