Casio CZ/ VZ/ FZ - Pro Series

me personally hate to be the bringer of
bad news
 but 
with my experience would take a guess
its your aftertouch contact strip in the
vz-1....

over time they become less sensitive
 due to tarnish or corrosion..
 
have it replaced or clean it yourself 

 see if this makes any noticeable
difference ,,,,,

it works on a pressure sensitive
resistance ...
and I suspect this is why u need to
press so hard (above 80)to get it to be
effective ,,,

have you tried using a sequencer and
sending controller data to the vz-1 just
to see if responces quicker to after
touch control?


ive been known to be wrong 
is a vz10 any good to do comparison
,that's all I have 

charles