Hello elektrofunk.
I've downloaded and sent your sysex file to my REV2 (16 voice), and it produces a similar behavior, though not as pronounced. All notes play on mine, but some are fainter then others, and of course it's always on the same voices (roundabout voice assignment).
So my conclusion is that it's because of pulse width calibration variations between voices. This is an analog synth, and although it has DCOs (digital frequency control of the oscillators), the waveshaper is analog and voltage controlled.
On my REV2, it came a time when the calibration procedure couldn't do a good enough job. I contacted DSI support, and they suggested clearing the calibration data table (which might have become corrupt).
You can do this by accessing the "debug menu" by holding "down" and "up" and pressing "global". The first item should be "1. Clear Calibration". To get out of that menu, simply press "global" again. Once it's done, power down the synth, wait 10 seconds, power it back, and call up the calibration. It might take longer to go through it since it will start from scratch on each voice. It might even lock-up at some point. If it does, simply wait at least 3 or 4 minutes to make sure it's really stuck, and power cycle the synth and restart another calibration. Everything should be fine after that.
It might, in the worst case, require more than one calibration to get things in order. But if after all of that the synth doesn't behave normally (within the bounds of acceptable minimal analog variations between voices), than DSI support should take over.
EDIT: after having a look at the patch itself, I noticed that you control the wave shape of OSC1 with ENV3 with maximum amount (in the mod matrix slot 1), even though the wave shape is already at 97%. Anytime you play with parameters on the edge like that, you're bound to encounter variations due to the analog nature of control voltage. After playing a little more with your patch, I discovered that when playing some lower keys on my REV2 there ARE a few notes that aren't producing sounds. Most probably because of calibration varations of my unit, too.
Not only that, but if you listen closely when holding a note down (one that produces a sound), you'll hear the timbre change abruptly at some point (especially on lower notes). This is probably due to the digital resolution limitation of the DAC that sends the converted control voltage to the waveshaper.
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