Production Studio 4K Audio Problem

When I plug into the XLR outs, I am getting some noise and a high pitched "whistle" that varies in frequency if I have any source audio playing. When I have nothing playing, and the Master and sources off, the noise stays constant. When I plug the XLR cables into another source, there is not any noise. Any ideas?

What are you plugging the ATEM's audio out into? And/or what connections are at the other end of the XLR out of the ATEM? Are they balanced or unbalanced? I had problems with bad noise/distortion when I plugged the audio outs into a mixer using unbalanced 1/4" TS connectors that went away when we switched to balanced 1/4" TRS cable

When I plug into the XLR outs, I am getting some noise and a high pitched "whistle" that varies in frequency if I have any source audio playing. When I have nothing playing, and the Master and sources off, the noise stays constant. When I plug the XLR cables into another source, there is not any noise. Any ideas?

Registered to post an answer, in case anyone else runs into this issue. I had the same issue, whistling sound when plugging both outputs on the ATEM into a mixer, and a lot of pink noise when plugging in only one output. What helped me solve this is realizing the ATEM is probably outputting a line level signal, and my mixer's XLR inputs are all mic level which meant I'm probably getting an impedence mismatch. So, I brought down the gain on my mixer inputs and the noise was gone.