In several American Revolt missions I can't navigate on the map. In Yukon and the Atlantic Accelerator, the view keeps scrolling in one direction, no matter what I do with the mouse and where I click on the mini-map. In Northwest Territories, I could stop the scrolling but was then stuck in one place and could not move anywhere else. Alaska works fine, and so do all the missions in the base game. Any idea what's going on here and what to do about it?

I'm using a MacBook with an external two-button mouse.