UE4 crashed cause of an assertion failed

Hi,

I tried to developp a small game with blueprints only.
And my UE4 crash regularly with this following message.

"
!Id:634f1e8f4d13ce25cbf53b7eaaa3c5e9

Unknown exception - code 00000001 (first/second chance not available)

Assertion failed: !HasAnyFlags(RF_NeedLoad|RF_NeedPostLoad) [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.4\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectLinker.cpp] [Line: 94]
Detaching from existing linker for C://Users//

KERNELBASE + 37901 bytes
UE4Editor_Core + 3095148 bytes
UE4Editor_Core + 1661722 bytes
UE4Editor_Core + 1541808 bytes
UE4Editor_CoreUObject + 1610740 bytes
UE4Editor_CoreUObject + 927331 bytes
UE4Editor_CoreUObject + 1108097 bytes
UE4Editor_CoreUObject + 1105561 bytes
UE4Editor_Engine + 1797805 bytes
UE4Editor_KismetCompiler + 329475 bytes
UE4Editor_KismetCompiler + 335318 bytes
UE4Editor_KismetCompiler + 343244 bytes
UE4Editor_KismetCompiler + 342018 bytes
UE4Editor_UnrealEd + 8984858 bytes
UE4Editor_Kismet + 595751 bytes
UE4Editor_Kismet + 834589 bytes
UE4Editor_Kismet + 854871 bytes
UE4Editor_Slate + 545350 bytes
UE4Editor_Slate + 1884845 bytes
UE4Editor_Slate + 1691884 bytes
UE4Editor_Slate + 2512538 bytes
UE4Editor_Slate + 2748777 bytes
UE4Editor_Slate + 794079 bytes
UE4Editor_Slate + 727433 bytes
UE4Editor_Core + 2503749 bytes
UE4Editor_Core + 2422753 bytes
UE4Editor_Core + 2508174 bytes
UE4Editor_Core + 2410066 bytes
user32 + 105425 bytes
user32 + 104666 bytes
UE4Editor_Core + 2509366 bytes
UE4Editor!FEngineLoop::Tick() + 2877 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.4\engine\source\runtime\launch\private\launchengineloop.cpp:2080]
UE4Editor!GuardedMain() + 476 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.4\engine\source\runtime\launch\private\launch.cpp:133]
UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.4\engine\source\runtime\launch\private\windows\launchwindows.cpp:125]
UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.4\engine\source\runtime\launch\private\windows\launchwindows.cpp:201]
UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]
"

What should I do?

Thanks for help,