Zoom automatically adjust volume while singing, although feature is turned of

I am a professional singer (soprano, singing mostly Opera i.e. Wagner and Verdi) and I am very, very loud. My current Zoom (on my thinkpad) during a voice lesson is always automatically adjusting the sound although it should not, because this feature has been deactivated in the audiosettings. It adjusts the volume so much that at the very loud parts my voice teacher no longer hears any tone at al. Although I am singing it does not transmit anything. As soon as I am only speaking it works like a dream... Why does this happen? I have already removed the tick at the communications tap of windows settings, but that does not change a thing... what is going on?