Clear incompetence in filling the DEF. I've now done a DEF refill twice in our Passat (after my free service expired), and spilled nary a drop. That bottle they sell at the dealer is supposedly spill-proof, but I use the M-B 10 liter jug w/ hose. The hose screws onto the filler neck in the trunk and is vented. Just set the jug on some suitable support and let it drain. When it's empty or stops draining, you're done*. Unhook and walk away. I got the M-B setup for $40 delivered on sale, and I just refill the jug with the $7 jug from Rural King, since DEF is DEF.
*It's probably wise to discard any leftover DEF, since the stuff is supposed to have a shelf life. At those prices, who cares?