The SampleTekk Classic Grand seems to be really heavy on resources! It sounds good, but playing it on its own through Rapture Session I'm constantly getting clicks (worse when I use the sustain pedal), and the "Classic Grand Bright" program range drops complete notes at random. When I run it through Sonar Pro, in addition to the clicks and dropped notes, it regularly crashes the sound engine (when playing this piano plus 2 other Rapture instruments simultaneously).
No other Rapture instruments have given me any trouble at all, so it's something specific to SampleTekk.
I'm running it at 44.1kHz through a UA-1G with buffering dialed up to max, on a Windows 10 quad i7 with 24Gb RAM plus SSD - what can I tweak to make it usable? I've observed it's only using 1 of the 8 virtual CPUs, and using it heavily.