Is Normal Zak no longer dropping things?

I've heard people complaining of it happening before this patch, as well.

I believe it's a form of party glitch. The game thinks you're not in the party that killed the boss, so you can't see its drops.
If that is the case, the drops should become visible after about 2:45 minutes. Try waiting it out?

I had this happen with Hilla the other day; I never even thought of that.