i am having a similar issue and have tried the suggestions in this thread and still am stuck. Last week, i was using it and the sequencer with no issues. Now, i have a stuck note - or, actually, indefinitely sounding notes. I would've posted a thread but i am new here so am replying to this one.
I have a grey Arp 2600 (no moog filter), 3620 keyboard, and ArpSequencer.
I have the initial gain all the way down, and i have notes that never stop. i am doing this without keyboard or sequencer connected. I have an infinitely sustaining note.
manual start fires as expected, and then the note just sustains forever. (when keyboard is connected, whatever the last note played is, that's what sustains forever.)
I can trigger my gates with sample and hold, and it acts as expected. I've patched my ADSR and AR to places to test those, and they work great.
Bottom line is, everything seems to be as expected, except for infinite sustaining note. any thoughts? Am i doing something wrong or do i need to get it looked at?