There is a tree on the marked tile, but game doesn’t draw it. I think it was there at the start of the battle but not sure. Now I can only see a tooltip about the tree and can’t stand on this tile. Don’t know if this bug is common because I don’t fight on 3rd levels often. But I’ll post screenshots here if this occurs again.
Sorry for screenshot, but I can’t take it properly. Game always show tooltip about fatigue instead of mouse cursor. I think it’s a bug too. First screenshot taken showed the global map (game was in the battle mode actually).