EQS Crash Assertion failed: !HasAnyFlags(RF_Unreachable)

Hi there. I got this error from crashing during standalone game. But it happens really randomly. It would really be great if someone can highlight where I can start looking to see what is causing the crash.

Assertion failed: !HasAnyFlags(RF_Unreachable) [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.9\Engine\Source\Runtime\CoreUObject\Private\UObject\ScriptCore.cpp] [Line: 905] 
EQSGenerator_UseContextAsLocation_C /Game/PC_Maps/Playtest1.Playtest1:EnvQueryManager_3.None  Function: '/Game/PC_Blueprints/AI/EQS/EQSGenerator_UseContextAsLocation.EQSGenerator_UseContextAsLocation_C:DoItemGeneration'

I have similar problem. Probably this is a garbage collector defect. I just used this method above in assertion ( HasAnyFlags(RF_Unreachable) ) on my object. Like a IsValidLowLevel().