I'm going to reply late to here but something to observe.

The Maths module is capable of doing offsets. So while your VCA knob may be all the way down, you may be leaking an offset into it that prevents it from fully closing.

On your Maths output, be sure to use the direct-out from channel #1 or channel #4 and not the mixer out. Use the output below the black box with the LED in it and not the outputs labeled "1" or "4" or "sum" etc. Then you'll be sure that your VCA fully closes.

This might not be the case... but it might be.