@mike175de
I think I found a temporary work-around as long as the underlying bug has not been fixed:
I disabled IOMMU by changing line
linux /vmlinuz-5.15.59-ipfire root=UUID=e8cf0bb4-4816-451b-ab5b-9ae2881097f0 ro panic=10 rd.auto
to
linux /vmlinuz-5.15.59-ipfire root=UUID=e8cf0bb4-4816-451b-ab5b-9ae2881097f0 ro panic=10 rd.auto iommu=off
in /boot/grub/grub.cfg
and then rebooted the system.
This disables the IOMMU feature completely which seems to fix the bug. Downside is, that the system then only sees 3.73GB RAM, so this can not be a permanent fix, but at least a work-around until the root cause is found and fixed (hopefully).
I switched to unstable yesterday, and got 171 update, issue resolved, no other issues detected. But this is just my home internet, take extra precautions if it is corporate network device.