@tnt Two things I'll note. Unless you are only testing, you should use the stable builds (not the unstable development community builds) located here: https://redirect.armbian.com/aml-s9xx-box/archive/
Second, in moving to the new armbian build framework post 23.02 release, there is an incompatible change in how the kernel .deb package is installed. After this change there no longer is a /boot/uImage file created. So the /boot/extlinux/extlinux.conf file will need to be changed if you upgrade to a later built kernel changing from uImage to Image. I don't know if this might be what you are running into, or some other instability in the development/unstable tree.