I had that problem however with the original bento and stem (see picture below, sorry for the dirty bike), and Canyon sent me a free bento replacement (haven't had the chance to try it out, as I wanted to go with the lower bento and different stem anyway). Try re-installing the bento? It might be possible to move it ever so slightly backwards.
FYI if anyone experiences the aeria ultimate stem rubbing and getting caught on the bento, I solved it this weekend. Had to take the bento off and sand down the rubber using a very coarse grit sandpaper on the right side where it was rubbing. It comes as a sharp angle at the corner so I smoothed the edge and took a couple mm off. After reinstalling the bento the handlebar now turns freely both directions. Very excited as I've now got it working exactly how I wanted.