I was able to drag a block too far when attempting to delete, exposing a non-toolbox bit on the side. This was Chrome/Desktop at about 1024 pixels wide.
I'm not seeing an immediate resolution to this, it's definitely related to jQuery UI though and the scroll setting. I don't see a way to limit the scroll to only being vertical. Will look into this more.
I was able to drag a block too far when attempting to delete, exposing a non-toolbox bit on the side. This was Chrome/Desktop at about 1024 pixels wide.