Hi Pricto,
Not sure if it's normal for the Erica Synths - Black Quad VCA to bleed, perhaps indeed the best is to check this out with Erica Synths. I don't have this particular module, so I can't test it for you. I have quite a few other Erica Synths modules but haven't notice any bleeding.
I do have a Black VCA though, so I just tested it to be sure but it doesn't bleed. So yes, perhaps better check with Erica Synths.
On the other hand, I have the Doepfer A-138p mixer and that one does bleed a little bit. If it's totally quiet in the room and I haven't opened the volume (completely at zero) of the channels then I still can hear them very far away. At the moment of writing, if I carefully listen, I can hear some sound now (the bleeding from the A-138p). I also just all switched the mute switches to mute but still can hear it a bit (the A-138p I am talking about here). But I don't have that with the Black VCA.
Not sure if this helps, better check with Erica Synths and please do let us know. Good luck and kind regards, Garfield Modular.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads