This is happening to me too. When I Upgraded and installed the real-tracks updates, including holds, and shots, I would start a song with the drums, then listen, now I would audition a bass, real track would generate and if I hit the recycle button so as not to force a re-generation of the drums and bass , the "new" instrument and drums would generate and play fine, bass 2 bars and stop. In 2009 this wasn't a problem, it's disjointing especially when you are manually typing rests etc.

http://johntafaromusic.blogspot.com