JABB Guitar issues

[rpearl]

I'm new to JABB, having used GPO for a few years. I recently acquired JABB, and I'm having some issues with the Nylon String Guitar - specifically, chords buzz, and there is a lot of distortion if more than one guitar is playing; sometimes there is distortion if only one is playing if it has more than four voices. I can reduce the Velocity, but that only changes the volume - doesn't really solve the problem. Anyone else come across this?

Thanks