Have a game where my sovereign's army kept wierdly attempting to go to another location other than that selected. It felt similar to the mountain bug (selecting to move when the camera view had a mountain in the foreground would sometimes select the mountain and then attempt to path to the other side of the mountain), but it kept appearing somewhat randomly on the same stack from then on.
Here's a save file where the effect will happen if the sovereign attempts to move directly East one square. The sovereign will move there, then automatically select a location offscreen to the west and use the rest of her movement going back that direction.
Initially a 0.90 game, but is repeatable from the same location in 0.91
Played ~20 hours over multiple games and this one stack seemed to be the only one exhibiting this problem. Very annoying and efectively ruined that game.