Hello Fabian, thank you. I think I have to investigate more on my Hardware site. Either I replace the old HW, or reinstall it from scratch to see, if its the HW? Thanks anyway for your support.
Based on my limited knowledge, it sounds like it might be a problem with initramfs or kernel. Have you tried these commands?:
update-initramfs -u -k all
update-grub
also I see vfio_virqfd is either not available or not loaded. Are you using passthrough for devices?