I don't have that issue between ver. 6 & 7 - not sure it's commonly experienced (would like to know if others feel this - could be there's a little less latency from my basic observations TBH) - quite a few others I know using 7 have not encountered this.
I'd be inclined to first attack it as a latency issue.
MIDI notes lined up perfectly in a DAW is outputting more notes than we have fingers in exact timings in testing - so it's not about Pianoteq not being able to fire multiple notes all at once perhaps. Unless the Casio keyboard is not able to send those notes without triggering some glissandi or the internal audio processing has some limitation.
Trying out different buffer sizes (in Pianoteq settings/devices panel) would be a quick path to finding if lower or higher latency helps with realism which may help with perception/accuracy of simultaneous fingering.
Coincidentally was just exchanging notes about the positive value of higher latency for piano realism with others today - certainly don't be afraid of trying higher latency.
Often the goal of zero is not the kindest to the sense of a real piano action. My onboard hardware is fast, so I like to see up to 20ms latency in the Pianoteq interface to give more physical accuracy to playing. YMMV - and a buffer giving 5ms might feel way better than one giving 1.3 or something quite low. I can get 1.3 at 64 buffer size.. but it feels crazy like a synth, and really throws my timing off the boat
Pianoteq Studio Bundle (Pro plus all instruments) - Kawai MP11 digital piano - Yamaha HS8 monitors
