I have ran into this issue before. @jkb was on the right track- it's actually an issue with window size and scrolling. The scroll is just very hard to activate here. Our development team is aware of this and it is in our backlog. For the meantime, I have had success with pressing and holding a zone in the list, like you were going to move it's order, then dropping it, then trying to scroll. For some odd reason this makes the scroll easier.