Sometimes it show the wrong movable tiles.
You can't actually move there but it is highlighted.

I'm not sure why or how but it happens recently.
some with creatures that became aloft just only for the last turn.

In an issue that may or may not be related, with the downloaded client I have recently started having trouble clicking on tiles in the upper right corner when I have the client maximized because the text box sits over them. You can resize the window or drag around the map to fix it once you realize what the problem is, but until then you are just left clicking on a tile, with no feedback about why your clicking isn't doing anything.