2. In the keymap, click on any region which seems to be \'lingering\'.
3. Now in the bottom right hand section of the screen look at case properties for Envelope 1\'s RELEASE value. That\'s the time it takes for the sampler to fade the sound to 0 after you release the key. It\'s probably set to some large number. If it\'s a piano style sound it should have a very low number for the release like, say, 0.1 seconds.
4. If this is the case you can rubber band all the offending regions and edit them simultaneously, then save to disk never to be lingered at again.