Cant think of a name

[Slastraf]

make a new script

Script.first = nil --entity
Script.second = nil --entity

function Script:Start()

if self.second == nil then System:Print(">> second is nil") end 

end

now drag two random things in each slot of the Script tab and run the game, nothing will happen.
then click on the red x of "first" so it will disappear.
Now for some reason, second will be nil when you run the game again.
I don't know if it has some more details for reproduction but I think this should be enough.