Dwarfs lose the ability to path to food. I actually had a dwarf die from hunger while surrounded by food. When I played from an earlier save, this problem only reappeared when the fort had about 230 dwarfs. The map was generated in 0.31.16 but the problem appeared while playing in 0.31.18. The only modifications that I have are, dwarf speed=0, changing the Dungeon Master to be electable by the expedition leader and mayor and to remove skill and attribute rust. I am using Maydays tileset.