Sometimes, a slow song with long notes - and also use of the Sustain pedal CC -- can overlap and certain softsynths don't respond fast enough. Although this is usually exhibited as "stuck" notes, I do recall a situation as you describe happening to me with a file when I was using the VSC synth.

PT and RB are so close to being the same MIDi engine and you say it works fine in PT but not in RB. Check the Preferences carefully in PT, jot them down if you have to, then check to see if RB is set up the exact same way. The MIDI Preferences is where I'd start. Also make sure that both are invoking the same softsynth that you are using in PT. Finally, just in case, don't try to have both programs open at the same time when testing this. Don't minimize one when opening the other, Close it down completely first.



--Mac