N.B. From experimentation I have determined that this problem is not a VSL issue.
Normally I use CC11 for local dynamic changes and CC7 for global dynamic settings. (see attached image).
Very occasionally however, for some reason, CC7 does nothing at all, and I can't see why. Vel XFade is on in the Perform settings, the patch Velocity XFade is set to global, but no CC7 changes have any effect on the sound. (CC11, CC1, etc. all work normaly).
Any ideas what is going wrong?