well, we just discussed this in this thread:
http://www.elektron-users.com/modules/newbb/viewtopic.php?topic_id=381&forum=1and decided that the sequencer does not automatically input note off - you need to put the note off info in yourself by holding function and hitting a step, which makes a yellow LED light - that signifies note off.
Or, you can do what I was doing before which is to tweak the Release and Decay until the notes become more staccato or to taste.