Track turns off automatically after a while

Hi, I#m Lutz,
I have an issue with multiple tracks on my cubase projects.
After a while some of them shut down - without changing any setting, tha would cause it. The problem could not be any automation, cause this is happening suddenly and not regulary. If I turn the tracks off and on a gain, it works for a few seconds, then I have the same issue as before.

My PC: intel core i7 9700k
Msi 390z Mainboard
Soundcard: Steinberg UR22 Mk2

So it shouldn’t be a problem caused by my PC.

Thanks for helping