Rapture Pro vel trk on filter envelope causes notes to hang

While playing around with some patches I had originally made in Rapture, I noticed that notes would hang when I set velocity tracking above 0 on the filter envelope.  Setting it back to 0 would stop the "hanging" notes.  I tried setting the amp envelope to a really short time, but it didn't stop the hanging notes or affect newly triggered notes.  Setting vel_trk below 0 seemed to work as expected.  This behavior was a little different on a patch I created from scratch.  With amp envelope off, the note would hang as soon as vel_trk was set above 0.  However, once I added an amp envelope, the patch would work as expected.  I did not get this behavior with Rapture which worked as expected in each case.  Anyone see anything like this?
 
This hanging behavior didn't occur with vel_int.  It was a little hard for me to understand what the difference between vel_trk and vel_int are from the documentation, but I got the impression that vel_int adjust the envelope scaling by velocity while vel_trk adjust the envelope offset by velocity.
 
This is occurring in Sonar X3 by the way.
Dan