Recording problem IRig stream with audacity

After having recorded my dj session when I listen to the recorded file I hear suddenly somewhere in the record a screaming noise which starts and stops without any reason…it starts after 15 minutes, after 1 hour , or after a certain undefined time. I have connected the IRig stream to the REC out at the back side of my mixer with 2 RCA cables and on the other side the IRig stream is plugged into my laptop with a USB C cable.
I have set the IRig stream as input and output device in audacity and I am not exceeding the noise level of - 9dBA. To be sure of that I am using the build-in noise level metering system of audacity during recording.
Has anybody had the same kind of problem or knows how I could solve it as I have tried everything without sucess.

The most common cause of screaming noise is a misconfiguration that creates a “feedback loop”.
A feedback loop occurs when there is an audio pathway from the output back into the input (which then goes back to the output, then loops back into the input, and round and round getting louder each time).

However, a feedback loop doesn’t “just suddenly happen” without the operator doing something to make it happen.