Help building the "DIY wine box theremin".

So, I am trying to build the wine box theremin (circuit found on this site). I'm not an eletronic engeneer, I don't have any grade on this science, all that I know I learn it myself. I managed to get all pitch part to work (I allmost can play the Midsommer Murders theme on it), but it's getting quite hard to get the volume side. Any help?

I noticed various comments where that was posted that the volume circuit doesn't seem to work, but no really useful responses. I'm also not having much luck finding Adrian Bontenbal, who would be the most likely person to be able to sort it out...

I found him :-)
"I have  build 2 wine box theremins, and they work perfectly.
The volume part is the difficult part. The volume oscillator frequency most be the same as  the filter part the incoming side of volume section. You have to experiment with small caps there."

This may also be helpful, it appears to be the design that the wine box theremin was originally based on: https://strangeapparatus.com/theremin

You can search Youtube for tutorials, they give various resources with practical advice.