I just witnessed this again on a DT2 running the latest 1.03A firmware yesterday. Not only was a second sound triggered upon release of the same button that was pressed, but it was a completely different sample than the one assigned to the channel.
Rebooting was the only action that made the behavior stop. This bug has not been fixed by firmware 1.03A.
EDIT: I recently got word that the team is aware of this bug, and that it’s being worked on. It’s related to sending notes from an external MIDI controller on the auto channel while switching channels (extremely common if you’re using another sequencer for MIDI input). No word on when that might be in a firmware update.