The Roland Juno 106 does not have a built-in midi “All notes off” button or function. If you get a stuck or hung note you need to either turn off the synth or use some outside midi tool to send the all notes off command.
I did find a work-around though – if you change the midi channel on the Juno 106 (press midi plus a bank number button), all voices will stop sounding.
As a side note, I’ve never experienced stuck or hung notes from the Juno itself. I only get them when using various sequencers and experimental code sending midi to the Juno.