Windranger unique attack modifiers don't work if you get Aghs afterwards..

So I'm trying to do that Windranger quest and am really dumb. First time playing that hero.

I didn't know that you need Aghs before you get anything like Desolator in order to get rid of the unique attack modifier constraint. However, in my game where I went deso first (again, because I'm dumb), and I got Aghs second, the deso wasn't applying the armor debuff. I checked on neutral creeps and yup, no armor debuff. I had to drop my items multiple times and repick them up before it started to work...

Anyone else notice this? Or maybe I'm imagining things...

EDIT: It was because I had two unique attach modifier items. Helm and Desolator. I'm now fully understanding "does not stack with other unique attack modifiers." Sorry for wasting your time but thank you for helping me learn! :P