Stack bugs (ingot bug)
dropping unIDed metal ingots can crash game
Game crashes when adom tries to stack certain items.
Commonly happens when extended dropping unIDed metal ingots.
It appears to be a matter of conflicting identification states being present in the same square (or in one's inventory), and for some reason the conflicting situation is most readily generated in-game by ingots.
Credit to RGRA bug list for description.