How to replicate? Have a wand of digging and cast it at a closed door. The animation travels over normal dungeon floor and disappears but when it hits door, the door changes (depending on angle) to black dash/either slashes/pipe - / \ | and stays that way.


The door works normally and it refreshes to proper symbol after opening or accessing any of the menus (inventory/drink potions/cast wands etc.) that replace current dungeon screen.