Well, all I can say is that with or without the polycarb sheild, there are 3 ghost reticules. And there was ghosting on the one I tried last summer as well. So that's 2/2 models I've seen with ghosting so far. Perhaps this is an issue with newer models, because the other person had bought his new not too long before the game. I bought mine used, and it's a fairly recent model as well.
I would venture that rather than being a "defective" model, perhaps they've changed their manufacturing processes (as in, to cut costs) since you got yours 2 years ago.