Placing an automatic dispenser with the output blocked by a tile causes the items to get stuck within the tile. Duplicants are able to retrieve the items, but they disappear from the resource list while stuck.
Additionally, after the bug first occurred but with my items still buried, I moved the dispenser 1 tile away which should have dropped the items in plain air, but they teleported into the tile anyway to join the first set of items.
Caused some confusion as to where 6 wort seeds disappeared to.
Place an automatic dispenser with a natural tile on top of the output pipe (the lower left/right tile). Drop an item in and it may disappear, though duplicants can pull the item out into a storage bin. Once an item is buried, other nearby dispensers (tested 1 tile distance) might also drop items into the bugged tile.