I disabled the build in audio and nothing happened. When I check the alsamixer no sound card is displayed anymore. Maybe I forgot a important detail. I have the HiFiBerry DAC+ RTC.
In my opinion there is a bug somewhere, because the Linux OS do not recognize the sound card with the „hifiberry-dacplus“ in /boot/config.txt but with „hifiberry-dac“.
If you want I can give you direct access to the raspberry.