[LAU] threadirqs suspected to cause xruns

Hello everyone, so I ran into trouble with a new machine I built recently. It appears to be that when I enable threadirqs or use an rt-Kernel, I am getting an xrun inferno. At first everything is fine but after a few seconds/minutes of playback I get thousands of xruns. I am on Manjaro (KDE), the kernels I tried so far are 5.8.3-2 - working ok'ish without threadirqs enabled 5.6.19_rt12-3 - bad 5.4.59_rt36-1 - bad The funny thing is that I had a nice running system at first (around two months ago) on the same machine, the xruns started suddenly out of the blue. (Kernel update?) Configuration is Ryzen 5 3600 B450 Aorus pro Motu 1248 Manjaro KDE I tried to higher the buffers to 2048, didn't help. I installed an USB2 PCIe card so that I could separate the usb audio interface from other stuff and prefer its IRQ with rtirq. Nothing helped. What could be wrong? I would love to hear your opinions Best regards Moshe Werner