Hi Pricto,
Ah yes... if you don't use an Audio interface with output to your external mixer then your output signal is "too hot". Eurorack signals have a higher audio voltage than the usual audio lines, so that might be one reason. Try to use an audio output interface module to provide a good signal level to your external mixer.
I know there are lots of members here who do this directly without an audio interface module, like you do at the moment but since you are a sound technician, I do think you should do it the proper way :-) I.e. with an audio interface module. But up to you of course.
Your description of the Black Quad VCA that the signal starts to appear only at about 11 o'clock onwards, that's what I roughly recognise and experience with my Black VCA too, so perhaps that's just Erica Synths?
I don't think you are too picky, checking on certain things and make sure that everything is all right, is in my opinion, not being picky.
Let me know what Erica Synths tells you about that Black Quad VCA and good luck. Kind regards, Garfield.
For review reports of Eurorack modules, please refer to https://garfieldmodular.net/ for PDF formatted downloads