If you’re using AI to try and find the closet item, then the best way to do it is EQS (Environment Query System) -
https://docs.unrealengine.com/latest/INT/Engine/AI/EnvironmentQuerySystem/
In that you could just get all actors of a class then score them based on distance to the querier. Try setting that up and seeing if that fixes your issues. I don’t entirely understand that node setup if you try to unset something from an actor that has been destroyed it will return none for the target, so at some point you’re referencing something that no-longer exists within the level.