I have this happen all the time. It happens whenever i'm right-click-panning, and let go of the right click when i'm not on the "actual surface", if that makes sense to you. Like, if i start right-click-panning on the map, then move my cursor over to the chat area and let go; every time i move my cursor over the map area it behaves as if i'm still right-clicking. It can be frustrating and disorienting if you don't know what's causing it. But all you have to do is right-click and then let go while your cursor is still over the map area. If you're super zoomed out it can be a particularly irritating thing, because you have to zoom-in, fix it, and then zoom back out. But it's not difficult to work around, once you know what to do.