Zeb3 key release weirdness

[Matfink]

Hey all I'm trying to track down (and remove) an oddity from the Z3 preset 'Elevation'.

Basically: on osc 2 if I play a chord then when I release the keys I get a quite audible sound like some envelope has retriggered or some voice re-activated. It's related to the lowest held key being released; a single key does not make the noise when released. Almost sounds like its a mono patch switching to the next higher note immediately with an envelope reset.
If I slowly release the keys from the highest then it's fine. Wondering if its voice steal or similar or maybe a bug?

I just can't track down where this is coming from. Zeroing envelope release fixes it but I don't want zero release on the sound. Changing to legato does not fix. The MSEG does not appear to retrigger...

Ed: actually Osc2 does appear to be behaving as mono...

[Matfink]

Ah found it: its the pitch mapper: enabling tuning with Source Key = Lowest seems to effect mono behaviour.
Is this intended? Feels like a bug.

Further investigation: Gemini says this is actually intended behaviour to allow duophony 'ARP Odyssey Style'.
Allowing for that, there's still the original problem of it jumping to another note when chord keys are released.