Hello,
It is a speciel VCA. I suggest you read all informations about them in the manual.
In the Default preset the VCA1 should be set to 63 and the VCA2 set to 0.
When both VCA's values is over 0, then sound will pass through no matter it's a manual or modulated value. I don't understand why you don't hear it on other presets. Please elaborate in case i have misunderstood anything. Screenshots can be helpful.