I haven’t rebootet the system yet. Maybe the screen is the cause. It has an old 15" CRT and is the only system that always wan’t shwowing the bootsplash and is now the only affected system. So my first idea was to disable the bootsplash:
ucr set grub/bootsplash='nosplash'
But I’ll also try to change the vga mode. This are the current values:
Graphical resolution for the boot menu, e.g. 1024x768 (width x height x colour depth in bits).
Controls the video mode in which the Linux kernel starts up, replacing the "vga=" boot option.