Board Thread:Questions and Answers/@comment-86.178.34.188-20130131003001/@comment-173.71.27.18-20130208102455

If the chest a sorter is going to place an item in is full, the item will jam in whatever machine it started out in (transposer, relay, filter, etc). I've had items get jammed in sorters as well, for unknown reasons, so check them. The sorter will look like it's active (like it does when it pushes an item through with a tag) if an item is jammed inside it. you can unjam it by breaking the tube downstream from it.