Amusingly, Google Translate understands this idiom and translates it non-literally into the equivalent English idiom: "the guy really doesn't have all his marbles".
There are so many English idioms with this same basic meaning that I doubt even Google knows them all. Let's see:
EN: "His elevator doesn't go all the way to the top."
DE: "Sein Aufzug nicht gehen den ganzen Weg nach oben."
As I suspected, looks pretty literal to me.