I can recover those missing patches by turn off the Modulation and Reverb effect that are reside in Z3ta2.
 
Only the patches that engage Modulation effect are not sounding.
 
But there is too many Patches that are not sounding when I first select!!!
 
Though I can solve the problem myself, but It's too tedious and cumbersome.
 
 By the way Is it just me?

can you give a few patch examples?

I found some of the patches are like "swells". They need a little time to develop. Also try a different area of the keyboard.