I tried to load up the engine and was greeted by this error messaged after it reached 18% any ideas on how to fix this as I can no longer use the engine?

Development Programming & Scripting
1

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

UE4Editor_Core!AssertFailedImplV() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:100]
UE4Editor_Core!FDebug::CheckVerifyFailedImpl() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\AssertionMacros.cpp:450]
UE4Editor_DerivedDataCache!operator<<() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Public\Containers\Array.h:1152]
UE4Editor_DerivedDataCache!FMemoryDerivedDataBackend::LoadCache() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\MemoryDerivedDataBackend.cpp:244]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseBootCache() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:651]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseNode() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:158]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseHierarchicalCache() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:430]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseNode() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:173]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseAsyncPut() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:341]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseNode() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:190]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseKeyLength() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:382]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::ParseNode() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:178]
UE4Editor_DerivedDataCache!FDerivedDataBackendGraph::FDerivedDataBackendGraph() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:91]
UE4Editor_DerivedDataCache!FDerivedDataBackend::Get() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataBackends.cpp:938]
UE4Editor_DerivedDataCache!FDerivedDataCacheModule::GetDDC() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Developer\DerivedDataCache\Private\DerivedDataCache.cpp:539]
UE4Editor_Core!FModuleManager::LoadModuleWithFailureReason() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Modules\ModuleManager.cpp:519]
UE4Editor_Core!FModuleManager::LoadModule() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Modules\ModuleManager.cpp:334]
UE4Editor_Core!GetDerivedDataCache() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\CoreMisc.cpp:103]
UE4Editor_Core!GetDerivedDataCacheRef() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Core\Private\Misc\CoreMisc.cpp:114]
UE4Editor_Engine!CompileGlobalShaderMap() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Engine\Private\ShaderCompiler\ShaderCompiler.cpp:4669]
UE4Editor!FEngineLoop::PreInitPreStartupScreen() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:2664]
UE4Editor!GuardedMain() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:127]
UE4Editor!GuardedMainWrapper() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:137]
UE4Editor!WinMain() [D:\Build\++UE4+Licensee\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:268]
UE4Editor!__scrt_common_main_seh() [d:\agent\_work\5\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll
2

Looks like cache corrupted, search for DerivedDataCache directory in project directory and also in windows user data AppData (locallowlevel i think) in Unreal Enigne directory you should find it and delete those.

Note, this will make engine to recompile all shaders to rebuild that cache, which may take a while.

3

Hi thanks for replying. Just to be clear this is not a problem with a specific project but whenever I load up the engine. In the DerivedDataCache the file there is called “Compressed.ddp”, is this the file you wanted me to delete because I tried that however nothing happened. Any other ideas?

thanks