I think what your saying, is the bar doesn't go down exactly the same way as it comes up. Maybe super heavy attempts.
Bars twist a little with mixed grip too. So I could see the plates hitting the curved areas a little funky, and then things go koo-coo from there.
Amazon: People also bought : Amazon.com : Soccer Shin Guards -Youth Sizes - by DashSport - Best Kids Soccer Equipment with Ankle Sleeves - Great for Boys and Girls : Sports & Outdoors
_________________________________________
you can kinda see it here: Der Deadlift Deadener! - YouTube
as the pathetic weight comes down, it hits the slanted area, then that ricochets the plate forward or back.
I found three YT video so far regarding this product; everyone is demostrating with 135/225 doing Touch and Go light dead lifts. Stupid
______________________________________________
3rd edit:
Even with heavier weight, you can see how it moves fore-and-aft and side-to-side
Deadlift Deadeners 500 - Demoed by Delroy McQueen - YouTube