If you don't like the sound of a jammer in a public jam session you can escape from this sound in several ways:
1. Start your jam in a private session
2. Tick the jammer channel to mute his sound
3. Use the zipped individual tracks to remix the desired channels
4. Quit the jam
5. Wait a bit for jammer withdraw

Oh if only the Security features worked i would create my own private jamms long ago